Change default logging level to WARNING

To avoid spam in the build.

Test: Presubmits
Change-Id: I45db6cd92babda7f83582fd438210cae02c54708

tools/releasetools/common.py

@@ -194,7 +194,7 @@ def InitLogging():
           '': {
               'handlers': ['default'],
               'propagate': True,
-              'level': 'INFO',
+              'level': 'WARNING',
           }
       }
   }