Improve isolation of DND providers

Specifically, a change in state from one DND provider
shouldn't result in another's state being cleared if they
aren't yet bound (or are intentionally unbound).

Fixes: 111251709
Test: cts, cts-verifier

Change-Id: I42a0ba935577e708d9df02e2a6d3620e42395a51
diff --git a/services/core/java/com/android/server/notification/ZenLog.java b/services/core/java/com/android/server/notification/ZenLog.java
index 6760875..b016faf 100644
--- a/services/core/java/com/android/server/notification/ZenLog.java
+++ b/services/core/java/com/android/server/notification/ZenLog.java
@@ -36,7 +36,8 @@
 
 public class ZenLog {
     private static final String TAG = "ZenLog";
-    private static final boolean DEBUG = Build.IS_DEBUGGABLE;
+    // the ZenLog is *very* verbose, so be careful about setting this to true
+    private static final boolean DEBUG = false;
 
     private static final int SIZE = Build.IS_DEBUGGABLE ? 100 : 20;