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: Id3e4bbf57966a08abc40223c70fda44ed5a85718
Merge "Add daemonize dependency to network_checker"