gfs2: don't lock sd_ail_lock in gfs2_releasepage

gfs2: don't lock sd_ail_lock in gfs2_releasepage

Patch d0d64c012cd83a3ec5e9c02ace717a6c7677d162 changed gfs2_releasepage
so that it held the sd_ail_lock spin_lock for most of its processing.
It did this for some mysterious undocumented bug somewhere in the
evict code path. But in the nine years since, evict has been reworked
and fixed many times, and so have the transactions and ail list.
I can't see a reason to hold the sd_ail_lock unless it's protecting
the actual ail lists hung off the transactions. Therefore, this patch
removes the locking to increase speed and efficiency, and to further help
us rework the log flush code to be more concurrent with transactions.

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