Add sepolicy for microdroid_mgr to read sysprop servicemanager.installed

Allow it to read the servicemanager.installed prop so servicemanager API
calls aren't stuck waiting for a servicemanager process to become ready.
There is no servicemanager process on microdroid.

Test: atest vm_accessor_test
Bug: 358427181

Change-Id: Id500dcf03461a1d911c95e5457118d7d8bc7f167
diff --git a/private/property_contexts b/private/property_contexts
index 41ae9a2..c74c373 100644
--- a/private/property_contexts
+++ b/private/property_contexts
@@ -239,7 +239,8 @@
 traced.oome_heap_session.count u:object_r:traced_oome_heap_session_count_prop:s0 exact uint
 
 # servicemanager properties
-servicemanager.ready    u:object_r:servicemanager_prop:s0 exact bool
+servicemanager.ready     u:object_r:servicemanager_prop:s0 exact bool
+servicemanager.installed u:object_r:servicemanager_prop:s0 exact bool
 
 # hwservicemanager properties
 hwservicemanager.       u:object_r:hwservicemanager_prop:s0