Be even more thorough parsing /etc/ovirt-plugins.d/

If we can't figure out which RPM owns a package, see whether or
not there's a package by that name before giving up on the plugins
page.

Change-Id: Iab5fcbae07e2bd9d49c041bca13baa22bde3be07
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=994825
Signed-off-by: Ryan Barry <rbarry@redhat.com>