Add nightly test for vgimportclone and querying of vgnames with duplicate pvs.

Add nightly test for vgimportclone and querying of vgnames with duplicate pvs.

Related to rhbz 697959.

This test fails prior to these two commits:
commit af112eb2c9a62c5d794df920218bd3ee291d5b25
Author: Zdenek Kabelac <zkabelac@redhat.com>
Date:   Thu Apr 21 13:15:26 2011 +0000

    Skip check for NULL before dm_free

    dm_free makes this test itself.

commit 91419c3e86bf9666aab2aa631faae1ba73e8d745
Author: Zdenek Kabelac <zkabelac@redhat.com>
Date:   Thu Apr 21 13:13:40 2011 +0000

    Fix use of released vgname and vgid