jfs: fix error path in ialloc

commit 8660998608cfa1077e560034db81885af8e1e885 upstream.

If insert_inode_locked() fails, we shouldn't be calling
unlock_new_inode().

Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
Tested-by: Michael L. Semon <mlsemon35@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>