now SocketServer uses the injected context

The context injected by logback into SocketServer is subsequently
injected into RemoteAppenderServerRunner.  The runner simply casts it to
LoggerContext before injecting it into the client object.
further reduced system timing sensitivity in SocketConnectorBase

When testing the exception reported by SocketConnectorBase after a
connection failure, the test now uses lock and associated condition to
avoid synchronization issues.
Merge branch 'master' of github.com:qos-ch/logback