qemu: RDMA migration support

qemu: RDMA migration support

This patch adds support for RDMA protocol in migration URIs.

USAGE: $ virsh migrate --live --migrateuri rdma://hostname domain qemu+ssh://hostname/system

Since libvirt runs QEMU in a pretty restricted environment, several
files needs to be added to cgroup_device_acl (in qemu.conf) for QEMU to
be able to access the host's infiniband hardware. Full documenation of
the feature can be found on QEMU wiki:
http://wiki.qemu.org/Features/RDMALiveMigration

Signed-off-by: Michael R. Hines <mrhines@us.ibm.com>
Signed-off-by: Jiri Denemark <jdenemar@redhat.com>