tests: Drop /private CWD prefix in commandhelper
tests: Drop /private CWD prefix in commandhelper

/tmp is a symbolic link to /private/tmp on macOS. That causes failures
in commandtest, because getcwd returns /private/tmp and the expected
output doesn't match to "CWD: /tmp".

Rathern than making a copy of commanddata solely for macOS, the /private
prefix is stripped.

Signed-off-by: Roman Bolshakov <e9c94dff02085feaa10f4659102d5bd952cb2e61@yadro.com>

jfehlig/libvirt,libvirt/libvirt,zippy2/libvirt,nertpinx/libvirt,andreabolognani/libvirt,andreabolognani/libvirt,fabianfreyer/libvirt,olafhering/libvirt,nertpinx/libvirt,crobinso/libvirt,fabianfreyer/libvirt,crobinso/libvirt,jfehlig/libvirt,fabianfreyer/libvirt,olafhering/libvirt,libvirt/libvirt,zippy2/libvirt,zippy2/libvirt,jfehlig/libvirt,jardasgit/libvirt,jardasgit/libvirt,fabianfreyer/libvirt,andreabolognani/libvirt,libvirt/libvirt,zippy2/libvirt,crobinso/libvirt,jardasgit/libvirt,nertpinx/libvirt,olafhering/libvirt,nertpinx/libvirt,jardasgit/libvirt,fabianfreyer/libvirt,andreabolognani/libvirt,jfehlig/libvirt,crobinso/libvirt,olafhering/libvirt,jardasgit/libvirt,nertpinx/libvirt,libvirt/libvirt,andreabolognani/libvirt