xfs: refactor log recovery check

Add a predicate to decide if the log is actively in recovery and use
that instead of open-coding a pagf_init check in the attr leaf verifier.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>