Add support for unaddressed port

Add support for unaddressed port

Neutron could create a port without the IP address when the network doesn't
have a subnet. In this case, neutron will have no L3 knowledgee and we need
remove the L3 filter on it but reserve the L2 filter if there is.
This patch will make L2 agent verify the fixed_ips before converting the
security-group-rules into firewall rules, L3 rules in it will be removed.
And filter like arp-spoofing will be disabled for this port.

Partially Implements: blueprint vm-without-l3-address
Change-Id: I5cd1fdfa13a7e57258be7251768eaa8ba64d486e