When spawning an Hyper-V instance with NICs having the vif_type "hyperv",
neutron will fail to bind the port to the Hyper-V host if the neutron
server doesn't have the "hyperv" mechanism driver installed and configured,
resulting in a PortBindingFailed exception on the nova-compute side.
When this exception is encountered, the logs will say to check the
neutron-server logs, but the problem and its solution are not obvious
or clear, resulting in plenty of questions / reports, all having the
same solution: is there an L2 agent on the host alive and reporting to
neutron, and if neutron Hyper-V agent is used, make sure to install
networking-hyperv and configure neutron-server to use the "hyperv"
mechanism_driver.
Change-Id: Idceeb08e1452413e3b10ecd0a65f71d4d82866e0
Closes-Bug: #1744032
b80c245ba5