Added support for allowing the user to set the notification driver


This PR adds support for the notification driver being set to either "no_op", "rpc", or "log".
Relates to : https://github.com/rcbops/chef-cookbooks/issues/651

Two new attributes are added in:
  +default["neutron"]["notification"]["driver"] = "no_op"
  +default["neutron"]["notification"]["topics"] = "notifications"

The driver is string matched on the driver type.


This PR also adds in the ability for the user to enable debug on the dhcp agent and the ability 
to enable "enable_metadata_network" only if "enable_isolated_metadata" is set as true. Additionally
the user can now set "dnsmasq_lease_max"

Two new attributes have also been added to the accomodate these new options:
  +default["neutron"]["metadata_network"] = "False"
  +default["neutron"]["dnsmasq_lease_max"] = 16777216