virt: Fix issue 463

SubdirList.__set_initset__() was modifying the contents of
a list while iterating over it.  This caused every-other
subdirectory to be skipped when building a flat tree list.

Signed-off-by: Chris Evich <cevich@redhat.com>
virt: Reduce extranious test-search debug

If a test cannot be found, the list of searched subdirectories
will be included in the exception.  Otherwise, assume users
aren't interested in seeing the entire tree every run.

Signed-off-by: Chris Evich <cevich@redhat.com>