BUG: Fix CLI extension test fixing SEM_LAUNCH_COMMAND

Following commit r21737 [1], CLIs tests have been updated to make
use SEM_LAUNCH_COMMAND so that their code is decoupled from Slicer
specific variables.

This commit ensure that SEM_LAUNCH_COMMAND is updated to consider additional
settings so that environment is properly set when running CLI modules test
bundled in extension.

[1] http://viewvc.slicer.org/viewvc.cgi/Slicer4?view=revision&revision=21737

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22100 3bd1e089-480b-0410-8dfb-8563597acbee