bug#26911: 25.2; eshell "cd .." doesn't work correctly with TRAMP

[Yegor Timoshenko]

Steps to reproduce:

M-x eshell
cd /user@remote.com:/
cd bin
cd ..
pwd

Expected output:

/user@remote.com:

Actual output:

/user@remote.com:/home/user

Reproducible in default Emacs 25.2 install:

In GNU Emacs 25.2.1 (x86_64-apple-darwin13.4.0, NS appkit-1265.21 Version 
10.9.5 (Build 13F1911))
 of 2017-04-21 built on builder10-9.porkrind.org
Windowing system distributor 'Apple', version 10.3.1504
Configured using:
 'configure --with-ns '--enable-locallisppath=/Library/Application
 Support/Emacs/${version}/site-lisp:/Library/Application
 Support/Emacs/site-lisp' --with-modules'