virttest.qemu_devices: Fix the QMP command for device unplug

Correct QMP command sends arguments as object ({'id': ...}) and not
as pure text.

Signed-off-by: Lukáš Doktor <ldoktor@redhat.com>
virttest.qemu_devices: Support strict_mode enforcing while qdev.insert

It might be beneficial to be able to override the strict_mode for single
device while inserting it.

Signed-off-by: Lukáš Doktor <ldoktor@redhat.com>
virttest.qemu_devices: Remove completed TODO comments

Signed-off-by: Lukáš Doktor <ldoktor@redhat.com>
Merge pull request #1419 from autotest/multi-disk-hotplug

Multi disk hotplug