qemu.tests.multi_disk_random_hotplug: Improve the hotplug/unplug logic

This version first initiate all hotplug/unplugs and then verifies the
results, which puts more stress on qemu.

Signed-off-by: Lukáš Doktor <ldoktor@redhat.com>
qemu.tests.multi_disk_random_hotplug: PEP8/Pylint fixups

Signed-off-by: Lukáš Doktor <ldoktor@redhat.com>
qemu.tests.multi_disk_random_hotplug: Parallel variant of this test

This patch adds parallel variant, which hotplugs multiple random disks
over multiple monitors simultaneously.

As qdev is not thread safe it was necessarily to put the locking here.

Signed-off-by: Lukáš Doktor <ldoktor@redhat.com>
qemu.tests.multi_disk_random_hotplug: Use data_dir to se get correct name

Set absolute path for disk images using data_dir.get_data_dir().

Signed-off-by: Lukáš Doktor <ldoktor@redhat.com>
qemu.tests.multi_disk_random_hotplug: Force strict_mode in parallel mode

Parallel mode of this test doesn't keep order of inserted devices, which
leads to devices ending up in different buses. Setting strict_mode = True
always enforces bus and addr.

Signed-off-by: Lukáš Doktor <ldoktor@redhat.com>
Merge pull request #9 from autotest/multi-disk-hotplug

Multi disk hotplug