gfs2: Remove unnecessary gfs2_rlist_alloc parameter

The state parameter of gfs2_rlist_alloc is set to LM_ST_EXCLUSIVE in all
calls, so remove it and hardcode that state in gfs2_rlist_alloc instead.

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