incident_service: only disallow untrusted access

Allow device-specific domains to access the incident_service.

Test: build
Bug: 156479626
Change-Id: I3b368c09087e2d3542b70be5aa22f8ef47392221
diff --git a/private/app_neverallows.te b/private/app_neverallows.te
index 66e9f69..1157187 100644
--- a/private/app_neverallows.te
+++ b/private/app_neverallows.te
@@ -257,3 +257,6 @@
   -untrusted_app_25
   -untrusted_app_27
 } mnt_sdcard_file:lnk_file *;
+
+# Only privileged apps may find the incident service
+neverallow all_untrusted_apps incident_service:service_manager find;