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/CacheReader.cpp b/lib/bcc/CacheReader.cpp
index a8e252b..e44f5b5 100644
--- a/lib/bcc/CacheReader.cpp
+++ b/lib/bcc/CacheReader.cpp
@@ -153,7 +153,7 @@
 
   if (memcmp(mpHeader->libbcc_build_time, libbcc_build_time, 24) != 0) {
     mpHeader->libbcc_build_time[24 - 1] = '\0'; // ensure terminated
-    LOGE("Build time mismatch: lib %s cached %s\n", libbcc_build_time,
+    LOGW("Build time mismatch: lib %s cached %s\n", libbcc_build_time,
          mpHeader->libbcc_build_time);
     return false;
   }