Add config option forcing hugepages memory backing
Add config option forcing hugepages memory backing

Setting 'libvirt_use_huge_pages' config option in nova.conf will result
in using QEMU's -mem-path option while spawning a VM.

This is necessary for DPDK vRouter support on Juno.

Change-Id: I2e8337f47d10689816c46971a97a6214e0322399
Partial-Bug: #1491525

Juniper/nova,Juniper/nova,Juniper/nova,Juniper/nova