Kill hung frame listeners on each verify networks event
Kill hung frame listeners on each verify networks event

Network checker relies on interrupt signal for its own
internal logic, so after interrupt is received - it will
do some parsing work and wont finish immediatly.

But before starting frame listeners in a new run - old frame
listeners may be not interrupted because mcollective failed
due timeout or any other not predicted problem.
So, we need to completely shutdown frame listeners with kill -9

Tested:
  Spawned bunch of - /usr/bin/python /usr/bin/net_probe.py -c listen.conf
  Executed network verification from UI - all old listeners were killed,
  verification succeeded.
  Also, executed same test with removed pid files in /var/run/net_probe folder

Change-Id: I7aa48d00b3f86827ba9860a3e3797ed5bd0eb713
Closes-Bug: 1466020

eayunstack/fuel-astute,stackforge/fuel-astute,eayunstack/fuel-astute,stackforge/fuel-astute