libvirt support to force convergence of live guest migration

libvirt support to force convergence of live guest migration

Busy enterprise workloads hosted on large sized VM's tend to dirty
memory faster than the transfer rate achieved via live guest migration.
Despite some good recent improvements (& using dedicated 10Gig NICs
between hosts) the live migration may NOT converge.

Recently support was added in qemu (version 1.6) to allow a user to
choose if they wish to force convergence of their migration via a
new migration capability : "auto-converge". This feature allows for qemu
to auto-detect lack of convergence and trigger a throttle-down of the
VCPUs.

This patch includes the libvirt support needed to trigger this
feature. (Testing is in progress)

Signed-off-by:  Chegu Vinod <chegu_vinod@hp.com>
Signed-off-by: Jiri Denemark <jdenemar@redhat.com>