logd: Add support for *.logd.filter

- Add device (ro.logd.filter), persistent (persist.logd.filter)
  properties to control the default filters
- Allow logcat -P default to produce expected results
- Allow logcat -P disable to produce expected results

Change-Id: I651cb705373ec1e88a99e4b9086da4f9668a468a
diff --git a/logd/main.cpp b/logd/main.cpp
index 13dda78..cf8cb8f 100644
--- a/logd/main.cpp
+++ b/logd/main.cpp
@@ -212,6 +212,7 @@
         // Anything that reads persist.<property>
         if (logBuf) {
             logBuf->init();
+            logBuf->initPrune(NULL);
         }
     }