Enables hairpin_mode for virtual bridge ports, allowing NAT reflection
Enables hairpin_mode for virtual bridge ports, allowing NAT reflection

* enables hairpin_mode on virtual bridge ports on instance spawn
* adds conntrack DNAT state criteria to fixed/fixed SNAT exception so reflected traffic SNATs
* updates get_interface ElementTree to work with Python 2.6/2.7
* fixes bug 933640

Change-Id: I63b3e91b41898fcffda8a288be503f9b740b4b4e

n0ano/gantt,n0ano/gantt