Add daemonize dependency to network_checker

https://pypi.python.org/pypi/daemonize/2.2.1

This is library used for creating system daemons in python,
we are currently starting listeners as daemons

Related to blueprint fuel-plugable-checks

Change-Id: I63e2524c26c3e854bdd9ca3e4ccd7d91adfeaf81
Merge "Add daemonize dependency to network_checker"