Ignore partially deleted images in getAllImages().

Change-Id: I028dabbf1a0b39177d0c52222cae177f5123442f
Bug-url: https://bugzilla.redhat.com/show_bug.cgi?id=905038
Signed-off-by: Eduardo <ewarszaw@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/12938
Tested-by: Elad Ben Aharon <eladba1990@gmail.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>