Flag for FGS bg start default value should be true.

By default the feature should be enabled.

Bug: 136219221
Test: atest cts/tests/app/src/android/app/cts/ActivityManagerFgsBgStartTest.java

Change-Id: I8cb628f156773ae0da5a6dee23b9602e272767de

services/core/java/com/android/server/am/ActivityManagerConstants.java

@@ -287,7 +287,7 @@ final class ActivityManagerConstants extends ContentObserver {
     // When the restriction is enabled, foreground service started from background will not have
     // while-in-use permissions like location, camera and microphone. (The foreground service can be
     // started, the restriction is on while-in-use permissions.)
-    volatile boolean mFlagBackgroundFgsStartRestrictionEnabled;
+    volatile boolean mFlagBackgroundFgsStartRestrictionEnabled = true;
 
     private final ActivityManagerService mService;
     private ContentResolver mResolver;
@@ -580,6 +580,9 @@ final class ActivityManagerConstants extends ContentObserver {
     }
 
     private void updateOomAdjUpdatePolicy() {
+
+
+
         OOMADJ_UPDATE_QUICK = DeviceConfig.getInt(
                 DeviceConfig.NAMESPACE_ACTIVITY_MANAGER,
                 KEY_OOMADJ_UPDATE_POLICY,