SystemLog: Don't keep Config as a member
SystemLog: Don't keep Config as a member

The instance is only used in the createAsyncAppender method to get the
value of core.asyncLoggingBufferSize.

Replace the Config instance with an int that is initialized in the
constructor.

Change-Id: I5528b4dc2b3e508cbac988cb7b5464cc2662a121

WANdisco/gerrit,qtproject/qtqa-gerrit,GerritCodeReview/gerrit,qtproject/qtqa-gerrit,qtproject/qtqa-gerrit,GerritCodeReview/gerrit,GerritCodeReview/gerrit,qtproject/qtqa-gerrit,qtproject/qtqa-gerrit,WANdisco/gerrit,GerritCodeReview/gerrit,qtproject/qtqa-gerrit,GerritCodeReview/gerrit,GerritCodeReview/gerrit,WANdisco/gerrit,WANdisco/gerrit,WANdisco/gerrit,GerritCodeReview/gerrit,WANdisco/gerrit,WANdisco/gerrit,GerritCodeReview/gerrit,qtproject/qtqa-gerrit