In kernel 4.7, the capability and capability2 classes were split apart
from cap_userns and cap2_userns (see kernel commit
8e4ff6f228e4722cac74db716e308d1da33d744f). Since then, Android cannot be
run in a container with SELinux in enforcing mode.

This change applies the existing capability rules to user namespaces as
well as the root namespace so that Android running in a container
behaves the same on pre- and post-4.7 kernels.

This is essentially:
  1. New global_capability_class_set and global_capability2_class_set
     that match capability+cap_userns and capability2+cap2_userns,
     respectively.
  2. s/self:capability/self:global_capability_class_set/g
  3. s/self:capability2/self:global_capability2_class_set/g
  4. Add cap_userns and cap2_userns to the existing capability_class_set
     so that it covers all capabilities.  This set was used by several
     neverallow and dontaudit rules, and I confirmed that the new
     classes are still appropriate.

Test: diff new policy against old and confirm that all new rules add
      only cap_userns or cap2_userns;
      Boot ARC++ on a device with the 4.12 kernel.
Bug: crbug.com/754831

Change-Id: I4007eb3a2ecd01b062c4c78d9afee71c530df95f

AIUI permissions should be in private unless they need to be public.

Bug: 25861755
Test: Boot device, create and remove a user, observe logs
Change-Id: I6c3521d50dab2d508fce4b614d51e163e7c8f3da

Test: Boot device, observe logs
Bug: 63740245
Change-Id: I1068304b12ea90736b7927b7368ba1a213d2fbae

Bug: 25861755
Test: Boot device, observe logs
Change-Id: I6c13430d42e9794003eb48e6ca219b874112b900
Merged-In: I6c13430d42e9794003eb48e6ca219b874112b900
(cherry picked from commit 47f3ed09)

Bug: 25861755
Test: Boot device, observe logs
Change-Id: I6c13430d42e9794003eb48e6ca219b874112b900