xfs: fix return of uninitialized value in variable error

xfs: fix return of uninitialized value in variable error

Source kernel commit: 3b6dd9a9aeeada19d0c820ff68e979243a888bb6

A previous commit removed a call to xfs_attr3_leaf_read that
assigned an error return code to variable error. We now have
a few early error return paths to label 'out' that return
error if error is set; however error now is uninitialized
so potentially garbage is being returned.  Fix this by setting
error to zero to restore the original behaviour where error
was zero at the label 'restart'.

Addresses-Coverity: ("Uninitialized scalar variable")
Fixes: 07120f1abdff ("xfs: Add xfs_has_attr and subroutines")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>