jfs: fix error path in ialloc

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>
Cc: stable@vger.kernel.org
Merge tag 'jfs-3.12' of git://github.com/kleikamp/linux-shaggy

Pull jfs bugfix from David Kleikamp:
 "Just a patch to fix an oops in an error path"

* tag 'jfs-3.12' of git://github.com/kleikamp/linux-shaggy:
  jfs: fix error path in ialloc