xfs: don't leak the retained da state when doing a leaf to node conversion

If a setxattr operation finds an xattr structure in leaf format, adding
the attr can fail due to lack of space and hence requires an upgrade to
node format.  After this happens, we'll roll the transaction and
re-enter the state machine, at which time we need to perform a second
lookup of the attribute name to find its new location.  This lookup
attaches a new da state structure to the xfs_attr_item but doesn't free
the old one (from the leaf lookup) and leaks it.  Fix that.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>