Replace an events loop at the communication service with single-shot
connection workers. This should help to avoid deadlock behaviour in situations
when user quits the connection to one server and tries to connect to another
one. The events loop required synchronization blocks which cause ANR in
the situation described above.

Change the server connection interface to contain a connecting stage
in a separate method. This is more just-in-case measure for situations
when the connection constructor shouldn't be blocking.

Change-Id: I941a4b67d965f6b1f76bc9975818e82aea12bf00