apparmor: Implement security hooks for the new mount API

apparmor: Implement security hooks for the new mount API

Implement hooks to check the creation of new mountpoints for AppArmor.

Unfortunately, the DFA evaluation puts the option data in last, after the
details of the mountpoint, so we have to cache the mount options in the
fs_context using those hooks till we get to the new mountpoint hook.

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: John Johansen <john.johansen@canonical.com>
cc: apparmor@lists.ubuntu.com
cc: linux-security-module@vger.kernel.org