Remove the test path of image service

The patch Iab90412ff4e793b0bb395b8ba8b6d35cef316dec moves the existing
test modules to tempest/tests/lib/services/image, but we forgot to
remove the empty path. Then this patch removes it for the cleanup.

Change-Id: I38a20a7095119a29872ef644ce4af2ae0d6a7396
1 file changed