gfs2: Fix marking bitmaps non-full

Reservations in gfs can span multiple gfs2_bitmaps (but they won't span
multiple resource groups).  When removing a reservation, we want to
clear the GBF_FULL flags of all involved gfs2_bitmaps, not just that of
the first bitmap.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Reviewed-by: Steven Whitehouse <swhiteho@redhat.com>