Add changes to bring up Keystore Certificate post processor.

Adds a system property which denotes the presence of a post processor.
Also adds the policies for the post processor service that is needed for
the processor to work correctly.

Test: manual check with test cert processor.
Bug: 361877215
Change-Id: I5feb0a250e2856189d5b4165187dcb415790e529
diff --git a/private/service_contexts b/private/service_contexts
index 7c3efc7..37652ae 100644
--- a/private/service_contexts
+++ b/private/service_contexts
@@ -399,6 +399,7 @@
 restrictions                              u:object_r:restrictions_service:s0
 rkpd.registrar                            u:object_r:rkpd_registrar_service:s0
 rkpd.refresh                              u:object_r:rkpd_refresh_service:s0
+rkp_cert_processor.service                u:object_r:rkp_cert_processor_service:s0
 role                                      u:object_r:role_service:s0
 rollback                                  u:object_r:rollback_service:s0
 rttmanager                                u:object_r:rttmanager_service:s0