parse-duration test output

[Bruno Haible]

Hi Bruce,

$ ./gnulib-tool --test --with-tests parse-duration
produces as part of the unit test output (on glibc/Linux with bash 4.2
and other platforms):

../../gltests/test-parse-duration.sh: line 68: warning: here-document at line 
52 delimited by end-of-file (wanted `_EOF_')
could not parse time:  
        err 22 - Invalid argument
PASS: test-parse-duration.sh

Can you please fix this? Gnulib unit tests should normally not
produce output when they pass.

Bruno