fix(logging) reduce overly vebose logging

It huurts performance on mobile. It can still be enabled by setting the level to
debug / trace.

logging_config.js

     // {@link #defaultLogLevel}:
     'modules/RTC/TraceablePeerConnection.js': 'info',
     'modules/statistics/CallStats.js': 'info',
+    'modules/sdp/SDPUtil.js': 'info',
+    'modules/xmpp/JingleSessionPC.js': 'info',
+    'modules/xmpp/strophe.jingle.js': 'info',
     'modules/xmpp/strophe.util.js': 'log'
 };