Use libvirt filters for network security

libvirt comes with the following network filters:
  no-arp-ip-spoofing, no-arp-mac-spoofing, no-ip-spoofing, no-mac-spoofing
nova implements the network filter nova-no-nd-reflection.
For shared network, use all the above 5 filters.
For non-shared network, use only no-arp-mac-spoofing, no-mac-spoofing, and nova-no-nd-reflection.
These filters add rules to the ebtables, and do not conflict with neutron security groups which use iptables.

Closes-rally-bug: DE789 DE701 DE714 DE505
Implements: rally-task TA5323
Not-in-upstream: true
Merge pull request #21 from CiscoSystems/de711

Use libvirt filters for network security