Adds Hyper-V serial console log

Introduces the VM serial output log feature to the Hyper-V Nova
Compute driver.

The VM serial port COM0 is redirected to a named pipe so that a
worker can take the VM output and write it to a file.

The VM serial output is then read from this file whenever the
console log command is issued.

Implements: blueprint hyper-v-console-log

Change-Id: I7d3132c0f934ac3e8d28315f4da766466612a6c0
Merge branch 'branch4' of https://github.com/adelina-t/nova into adelina-t-branch4

Conflicts:
	nova/tests/virt/hyperv/test_hypervapi.py
	nova/tests/virt/hyperv/test_vmutils.py
	nova/virt/hyperv/ioutils.py
	nova/virt/hyperv/vmutils.py

Change-Id: Ia3af99d487ca71a1319d21e5899411bf053e91b8
Merge branch 'adelina-t-branch4' into bp/hyper-v-console-log