Add prop for enabling system services

Added system_service_enable_prop domain for properties that could
enable/disable system services.

Bug: 340928990
Test: Local build + confirm bic not starting + presubmit
Ignore-AOSP-First: need to submit with changes in clockwork
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:09983fc534f280ac9a79f552eee5a473f2220df1)
Merged-In: Ife9041d30f10f2fbe7ab4cbcee1397901a21f0fb
Change-Id: Ife9041d30f10f2fbe7ab4cbcee1397901a21f0fb
diff --git a/private/system_server.te b/private/system_server.te
index e7ae9fc..1298bf7 100644
--- a/private/system_server.te
+++ b/private/system_server.te
@@ -900,6 +900,9 @@
 # configuration properties
 get_prop(system_server, sensors_config_prop)
 
+# Allow system server to determine if system services are enabled
+get_prop(system_server, system_service_enable_prop)
+
 # Create a socket for connections from debuggerd.
 allow system_server system_ndebug_socket:sock_file create_file_perms;