[GFS2] Fix bz 234168 (ignoring rgrp flags)

Ths following patch makes GFS2 use the rgrp flags properly. Although
there are also separate flags for both data and metadata as well, I've
not implemented these as there seems little use for them. On the
otherhand, the "noalloc" flag is generally useful for future changes we
might which to make, so this ensures that we interpret it correctly.

In addition I fixed the comment above the function which was incorrect.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>