gfs2: switch to lockref_init(..., 1)

In qd_alloc(), initialize the lockref count to 1 to cover the common
case.  Compensate for that in gfs2_quota_init() by adjusting the count
back down to 0; this only occurs when mounting the filesystem rw.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>