[RJA-2372][fix]: Made file attachments serializable
to be possible to send them in remote action result(from agent to backend).
[RJA-2342][fix]: Fail step execution in case of unexpected exception
in action executor actor
[RJA-2342][fix] - Race condition when checking agent status]
[RJA-2342][fix] - Imports cleaned
Merge pull request #987 from rsvato/Release_2_2_0

Cherry pick for critical fixes