[release] Prepare for next development iteration

Change-Id: I6211e46c8971e02c468b74c62f7952a9ea396df0
avoid concatenation in log calls using String concatenation

Change-Id: I1027def3135892bcd73cda6108e7b4c34244dbb3
Synchronization in websocket session to avoid condition races

Change-Id: I9114597bda547ec65e22b0e7995674109228b911
Fix bug in synchronization of websocket

Change-Id: I4a6c2c2dd5bcdc995375e68e93faabfee99adf47
[release] 4.2.1

Change-Id: Ie7dd88db3c84ac5f0b5fa5f27a4777fa3828b07f