Add limited support for Quantum+OVS on XS/XCP.

 * Add priliminary support for running the OVS L2 and DHCP agents
   in domU:
   * Configure Nova to use the correct vif driver and integration
     bridge.
   * Configure the ovs agent to target the dom0 integration bridge.
   * Install a xapi plugin supporting dom0 execution of ovs agent
     commands.
 * Config doc: http://wiki.openstack.org/QuantumDevstackOvsXcp
 * Supports blueprint xenapi-ovs

Change-Id: If5ab07daab1dc3918004eb4bfb6fed6cab0a71fd
Add basic uec image preparation to tempest

Add uec image preparation to lib/tempest.
cirros as image is hard coded at the moment.

If the images does not exists or the system is not able to use uec images the
image prepare step will be skipped and tempest will skip the related
tests as well.

Setting ssh username correctly.
Setting instance type for the boto test.

Change-Id: I0d36ac7834e1eb677007e2c92dfc375d134a6023
Merge "Add limited support for Quantum+OVS on XS/XCP."
Merge "Add basic uec image preparation to tempest"