xfs: push down inactive transaction mgmt for remote symlinks

Push down the transaction management for remote symlinks from
xfs_inactive() down to xfs_inactive_symlink_rmt(). The latter is
cleaned up to avoid transaction management intended for the
calling context (i.e., trans duplication, reservation, item
attachment).

Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Ben Myers <bpm@sgi.com>