apparmor: fix: kzalloc perms tables for shared dfas

Currently the permstables of the shared dfas are not shared, and need
to be allocated and copied. In the future this should be addressed
with a larger rework on dfa and pdb ref counts and structure sharing.

BugLink: http://bugs.launchpad.net/bugs/2017903


Fixes: 217af7e2 ("apparmor: refactor profile rules and attachments")
Cc: stable@vger.kernel.org
Signed-off-by: John Johansen <john.johansen@canonical.com>
Reviewed-by: Jon Tourville <jontourville@me.com>