sepolicy: Add rules for non-init namespaces

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
diff --git a/private/vold_prepare_subdirs.te b/private/vold_prepare_subdirs.te
index 3f17ce5..7bdcd84 100644
--- a/private/vold_prepare_subdirs.te
+++ b/private/vold_prepare_subdirs.te
@@ -7,7 +7,7 @@
 allow vold_prepare_subdirs vold:fd use;
 allow vold_prepare_subdirs vold:fifo_file { read write };
 allow vold_prepare_subdirs file_contexts_file:file r_file_perms;
-allow vold_prepare_subdirs self:capability dac_override;
+allow vold_prepare_subdirs self:global_capability_class_set dac_override;
 allow vold_prepare_subdirs self:process setfscreate;
 allow vold_prepare_subdirs system_data_file:dir { open read write add_name remove_name };
 allow vold_prepare_subdirs vold_data_file:dir { create open read write search getattr setattr remove_name rmdir };