Allow PackageManager to communicate to apexd.

This is used for querying the installed packages, as well as
coordinating the installations of packages.

Test: ran an app that queries PM, that queries apexd.
Bug: 117589375
Change-Id: I38203ffe6d0d312d6cc38e131a29c14ace0ba10c

private/system_server.te

@@ -941,6 +941,10 @@ allow system_server system_server_startup:fd use;
 allow system_server system_server_startup_tmpfs:file { read write map };
 allow system_server system_server_startup:unix_dgram_socket write;
 
+# Allow system server to communicate to apexd
+allow system_server apex_service:service_manager find;
+allow system_server apexd:binder call;
+
 # dexoptanalyzer is currently used only for secondary dex files which
 # system_server should never access.
 neverallow system_server dexoptanalyzer_exec:file no_x_file_perms;

public/apexd.te

@@ -6,8 +6,8 @@ binder_use(apexd)
 add_service(apexd, apex_service)
 set_prop(apexd, apexd_prop)
 
-neverallow { domain -init -apexd } apex_service:service_manager find;
-neverallow { domain -init -apexd } apexd:binder call;
+neverallow { domain -init -apexd -system_server } apex_service:service_manager find;
+neverallow { domain -init -apexd -system_server } apexd:binder call;
 
 neverallow domain apexd:process ptrace;