Keystore 2.0: Add permissions and policy for user manager AIDL.

Bug: 176123105
Test: User can set a password and unlock the phone.
Change-Id: I96c033328eb360413e82e82c0c69210dea2ddac9
diff --git a/private/service_contexts b/private/service_contexts
index 502403c..0c6e475 100644
--- a/private/service_contexts
+++ b/private/service_contexts
@@ -33,6 +33,7 @@
 android.security.identity                 u:object_r:credstore_service:s0
 android.security.keystore                 u:object_r:keystore_service:s0
 android.security.remoteprovisioning       u:object_r:remoteprovisioning_service:s0
+android.security.usermanager              u:object_r:usermanager_service:s0
 android.service.gatekeeper.IGateKeeperService    u:object_r:gatekeeper_service:s0
 android.system.keystore2                  u:object_r:keystore_service:s0
 app_binding                               u:object_r:app_binding_service:s0