xfs: don't ASSERT on short form btree root pointer of zero

Don't ASSERT if the short form btree root pointer is zero.  Now that we
use xfs_verify_agbno to check all short form btree pointers, we'll let
that log the error and pass it to the upper layers.
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

fs/xfs/libxfs/xfs_alloc_btree.c

@@ -242,7 +242,6 @@ xfs_allocbt_init_ptr_from_cur(
 	struct xfs_agf		*agf = XFS_BUF_TO_AGF(cur->bc_private.a.agbp);
 
 	ASSERT(cur->bc_private.a.agno == be32_to_cpu(agf->agf_seqno));
-	ASSERT(agf->agf_roots[cur->bc_btnum] != 0);
 
 	ptr->s = agf->agf_roots[cur->bc_btnum];
 }

fs/xfs/libxfs/xfs_refcount_btree.c

@@ -192,7 +192,6 @@ xfs_refcountbt_init_ptr_from_cur(
 	struct xfs_agf		*agf = XFS_BUF_TO_AGF(cur->bc_private.a.agbp);
 
 	ASSERT(cur->bc_private.a.agno == be32_to_cpu(agf->agf_seqno));
-	ASSERT(agf->agf_refcount_root != 0);
 
 	ptr->s = agf->agf_refcount_root;
 }

fs/xfs/libxfs/xfs_rmap_btree.c

@@ -234,7 +234,6 @@ xfs_rmapbt_init_ptr_from_cur(
 	struct xfs_agf		*agf = XFS_BUF_TO_AGF(cur->bc_private.a.agbp);
 
 	ASSERT(cur->bc_private.a.agno == be32_to_cpu(agf->agf_seqno));
-	ASSERT(agf->agf_roots[cur->bc_btnum] != 0);
 
 	ptr->s = agf->agf_roots[cur->bc_btnum];
 }