AppArmor: Fix splitting an fqname into separate namespace and profile names

As per Dan Carpenter <error27@gmail.com>
  If we have a ns name without a following profile then in the original
  code it did "*ns_name = &name[1];".  "name" is NULL so "*ns_name" is
  0x1.  That isn't useful and could cause an oops when this function is
  called from aa_remove_profiles().

Beyond this the assignment of the namespace name was wrong in the case
where the profile name was provided as it was being set to &name[1]
after name  = skip_spaces(split + 1);

Move the ns_name assignment before updating name for the split and
also add skip_spaces, making the interface more robust.

Signed-off-by: John Johansen <john.johansen@canonical.com>
Signed-off-by: James Morris <jmorris@namei.org>