gfs2: Make sure we don't miss any delayed withdraws

Commit ca399c96 changes gfs2_log_flush to not withdraw the
filesystem while holding the log flush lock, but it fails to check if
the filesystem needs to be withdrawn once the log flush lock has been
released.  Likewise, commit f05b86db depends on gfs2_log_flush to
trigger for delayed withdraws.  Add that and clean up the code flow
somewhat.

In gfs2_put_super, add a check for delayed withdraws that have been
missed to prevent these kinds of bugs in the future.

Fixes: ca399c96 ("gfs2: flesh out delayed withdraw for gfs2_log_flush")
Fixes: f05b86db ("gfs2: Prepare to withdraw as soon as an IO error occurs in log write")
Cc: stable@vger.kernel.org # v5.7+: 462582b9: gfs2: add some much needed cleanup for log flushes that fail
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>