BUG-731 : refactored stateful listeners

- moved nullchecks for input LSP to separate method (should fix most complexity warnings)
- moved MBB procedure to separate method

Change-Id: Icf791b41dedb408340fe4cbe2e439bceab1c1b30
Signed-off-by: Dana Kutenicsova <dkutenic@cisco.com>
Merge "BUG-731 : refactored stateful listeners"