COMETD-474 (ReloadExtension doesn't clear state if server is down at the moment of disconnection).

Modified reload extension to clear state also on outgoing disconnect.
Inherited @Deprecated annotation.
COMETD-498 (Publish callbacks are not invoked for locally failed messages).

Fixed by ensuring that locally failed messages have a message ID,
which is the key to the callbacks map.
COMETD-474 (ReloadExtension doesn't clear state if server is down at the moment of disconnection).

Modified reload extension to clear state also on outgoing disconnect.
Merged branch '2.8.x' into 'master'.