report the command line when a test case is failed

Like this:
Testing Units/option-langmap-ext--pat-ext...passed
Testing Units/option-langmap-pat--ext...FAILED
	differences left in Units/option-langmap-pat--ext.d/DIFF.TMP
	cmdline:  ./ctags --options=NONE --data-dir=Data ...
Testing Units/option-langmap-pat--pat-ext...passed

Signed-off-by: Masatake YAMATO <yamato@redhat.com>