bug#41423: 27.0.91; tramp regression on pretest

[rrandresf]

1. emacs -Q
2. Evaluate snippet below:
--8<---------------cut here---------------start------------->8---
(let ((default-directory "/ssh:user@5quince:~/")) (eshell))
--8<---------------cut here---------------end--------------->8---
3.  On the eshell buffer I do
--8<---------------cut here---------------start------------->8---
cd dev/c/h {hit TAB key for getting completion do its job and press Return key}
--8<---------------cut here---------------end--------------->8---

Observation: On emacs-26.3 it is inmediate. But on pretest it takes almost 3m to
complete same the action.

andres.ramirez
ps: just in case completion does cd dev/c/hildon/


In GNU Emacs 27.0.91 (build 1, armv7l-unknown-linux-gnueabihf, X toolkit, Xaw3d 
scroll bars)
System Description: Arch Linux ARM

Recent messages:
Loading em-basic...done
Loading em-cmpl...done
Loading em-dirs...done
Loading em-glob...done
Loading em-hist...done
Loading em-ls...done
Loading em-prompt...done
Loading em-script...done
Loading em-term...done
Loading em-unix...done
#<buffer *eshell*>
Configured using:
 'configure '--program-transform-name=s/^ctags$/ctags.emacs/'
 --prefix=/usr --sysconfdir=/etc --libexecdir=/usr/lib
 --localstatedir=/usr/share --with-x-toolkit=lucid
 --mandir=/usr/share/man --pdfdir=/usr/share/doc/emacs --with-modules
 --with-xft --without-gconf --without-gsettings --with-imagemagick
 --without-xwidgets --without-pop --with-gameuser=:games
 --disable-build-details 'CFLAGS=-march=armv7-a -mfloat-abi=hard
 -mfpu=vfpv3-d16 -O2 -pipe -fstack-protector-strong -fno-plt'
 CPPFLAGS=-D_FORTIFY_SOURCE=2
 LDFLAGS=-Wl,-O1,--sort-common,--as-needed,-z,relro,-z,now'

Configured features:
XAW3D XPM JPEG TIFF GIF PNG RSVG IMAGEMAGICK SOUND GPM DBUS GLIB NOTIFY
INOTIFY ACL GNUTLS LIBXML2 FREETYPE HARFBUZZ M17N_FLT LIBOTF XFT ZLIB
TOOLKIT_SCROLL_BARS LUCID X11 XDBE XIM MODULES THREADS LIBSYSTEMD JSON
PDUMPER LCMS2 GMP

Important settings:
  value of $LC_COLLATE: C
  value of $LANG: C
  locale-coding-system: nil

Major mode: Eshell

Minor modes in effect:
  eshell-prompt-mode: t
  eshell-hist-mode: t
  eshell-pred-mode: t
  eshell-cmpl-mode: t
  eshell-proc-mode: t
  eshell-arg-mode: t
  shell-dirtrack-mode: t
  tooltip-mode: t
  global-eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message rmc puny dired dired-loaddefs
rfc822 mml mml-sec epa derived epg epg-config gnus-util rmail
rmail-loaddefs text-property-search mm-decode mm-bodies mm-encode
mail-parse rfc2231 mailabbrev gmm-utils mailheader sendmail rfc2047
rfc2045 ietf-drums mm-util mail-prsvr mail-utils pcmpl-unix em-unix
em-term term easymenu ehelp em-script em-prompt em-ls em-hist em-pred
em-glob em-dirs esh-var em-cmpl em-basic em-banner em-alias tramp-cache
tramp-sh esh-mode eshell esh-cmd esh-ext esh-opt esh-proc esh-io esh-arg
esh-module esh-groups esh-util tramp tramp-loaddefs trampver
tramp-integration files-x tramp-compat shell pcomplete comint ansi-color
ring parse-time iso8601 time-date ls-lisp format-spec auth-source cl-seq
eieio eieio-core cl-macs eieio-loaddefs cl-loaddefs cl-lib
password-cache json subr-x map seq term/screen term/xterm xterm byte-opt
gv bytecomp byte-compile cconv disp-table tooltip eldoc electric
uniquify ediff-hook vc-hooks lisp-float-type mwheel term/x-win x-win
term/common-win x-dnd tool-bar dnd fontset image regexp-opt fringe
tabulated-list replace newcomment text-mode elisp-mode lisp-mode
prog-mode register page tab-bar menu-bar rfn-eshadow isearch timer
select scroll-bar mouse jit-lock font-lock syntax facemenu font-core
term/tty-colors frame minibuffer cl-generic cham georgian utf-8-lang
misc-lang vietnamese tibetan thai tai-viet lao korean japanese eucjp-ms
cp51932 hebrew greek romanian slovak czech european ethiopic indian
cyrillic chinese composite charscript charprop case-table epa-hook
jka-cmpr-hook help simple abbrev obarray cl-preloaded nadvice loaddefs
button faces cus-face macroexp files text-properties overlay sha1 md5
base64 format env code-pages mule custom widget hashtable-print-readable
backquote threads dbusbind inotify lcms2 dynamic-setting
font-render-setting x-toolkit x multi-tty make-network-process emacs)

Memory information:
((conses 8 141067 10597)
 (symbols 24 9524 1)
 (strings 16 41154 2442)
 (string-bytes 1 1131300)
 (vectors 8 19393)
 (vector-slots 4 599625 10098)
 (floats 8 51 242)
 (intervals 28 265 162)
 (buffers 576 13))