xfs_repair: skip block reservation when fixing freelist

xfs_repair: skip block reservation when fixing freelist

AGFL blocks are considered to be part of the fdblocks count, so there's
no need to obtain a block reservation when fixing the AGFL as part of
repair.  Asking for a reservation can cause repair to fail if the
superblock claims zero fdblocks because we haven't gotten far enough
into phase 5 to have reset the superblock counters.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>