qemu: Implement request of vCPU state using the guest agent
qemu: Implement request of vCPU state using the guest agent

https://bugzilla.redhat.com/show_bug.cgi?id=924400

This patch implements the VIR_DOMAIN_VCPU_AGENT flag for the
qemuDomainGetVcpusFlags() libvirt API implementation.
(cherry picked from commit c6afcb052c1ea4dd991e7e7873702bf8ba352e99)

Conflicts:
	src/qemu/qemu_driver.c: driver locking and domain obj simplification
                            not backported

mithleshvrts/libvirt-0.10.2,mithleshvrts/libvirt-0.10.2,mithleshvrts/libvirt-0.10.2,mithleshvrts/libvirt-0.10.2,mithleshvrts/libvirt-0.10.2