BACKPORT: selinux: wrap AVC state

Wrap the AVC state within the selinux_state structure and
pass it explicitly to all AVC functions.  The AVC private state
is encapsulated in a selinux_avc structure that is referenced
from the selinux_state.

This change should have no effect on SELinux behavior or
APIs (userspace or LSM).

Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Reviewed-by: James Morris <james.morris@microsoft.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>

(cherry picked from commit 6b6bc6205d98796361962ee282a063f18ba8dc57)
Resolved conflicts around non-backported sctp feature.
Change-Id: I6412982af61be2d76e747a942d011be2f0bb2528
Bug: 140252993
Signed-off-by: Jeff Vander Stoep <jeffv@google.com>