Add qemu-* command test cases

The qemu-* commands are explicitly unsupported in RHEL products, so
the testing strategy is mainly focus on return status and libvirtd status after
command been executed.

This depends on PR:
https://github.com/autotest/virt-test/pull/1666
@yumingfei the qemu_monitor module is for monitor cmd direct to qemu monitor, while virsh commands is using libvirt API to interact with qemu monitor. As we need test virsh command here, so add the testing case here. Hope I explain it clear :)