For b/3381327: Save 159+ms for every launch of Books, YouTube, Movie Studio...

Before this CL, you will see in the logcat:
  698 StopWatch D StopWatch calcFileSHA1 time (us): 159162
  698 bcc I File opened. fd=45
  698 bcc I File closed. fd=45
  698 StopWatch D StopWatch calcFileSHA1 time (us): 19282
  ...
This CL also cleans up bcc's logcat.

Change-Id: I4e23b459eee0dc77ef186fb761a64d731a721517
diff --git a/lib/bcc/ContextManager.cpp b/lib/bcc/ContextManager.cpp
index ea8c8b1..8d173c1 100644
--- a/lib/bcc/ContextManager.cpp
+++ b/lib/bcc/ContextManager.cpp
@@ -119,7 +119,7 @@
   }
 
   if (ContextSlotTaken[slot]) {
-    LOGE("Suggested bcc context slot has been occupied.\n");
+    LOGW("Suggested bcc context slot has been occupied.\n");
     return NULL;
   }