Improve logging in NetconfClient, logging-bridge. Increase connection timeout in sal-netconf-connector.

Stop polluting log file with unnecessary 'Exception' messages by logging-bridge, print stack trace with exceptions using slf4j.
Increase connection timeout in sal-netconf-client from 5s to 20s.
Include label in NetconfClient exceptions.

Change-Id: If6819029fb79ea6ebead6b6745adf2c439d107da
Signed-off-by: Tomas Olvecky <tolvecky@cisco.com>
Merge "Improve logging in NetconfClient, logging-bridge. Increase connection timeout in sal-netconf-connector."