qemu.tests.virtio_console: Use correct keywords for start_vm

start_vm should accept yes/no instead of 0

Signed-off-by: Lukáš Doktor <ldoktor@redhat.com>
qemu.tests.virtio_console: Force new params in vm.create()

This test started with "start_vm = no" and we are starting the VM
manually. It's not guaranteed, that params were updated in preprocess
so we need to make sure params were updated by calling create with
new params.

One example of incorrect params is when VM exists and is alive from
previous test. In such case preprocess skips initialization (start_vm
= no") and vm.create() destroys and recreates the VM from previous test.

Signed-off-by: Lukáš Doktor <ldoktor@redhat.com>
virttest.qemu_virtio_port: Check both size and presence of guest script

This patch adds additional check for compiled guest script file.
Sometimes the script exists in the guest machine, and has the correct
version, but wasn't successfully compiled. Originally this wouldn't be
dettect and compilation wouldn't be executed, making all following
tests to fail.

Signed-off-by: Lukáš Doktor <ldoktor@redhat.com>
virttest.qemu_vm: Return the qemu output when it defuncts during .create()

The new defunct() check in VM.create() returns only custom message.
Some negative tests need also the original qemu_output(). This patch
adds this output into the exception.

Additionally it catches the problems when the original PID doesn't exsit
(qemu died very quickly).

Signed-off-by: Lukáš Doktor <ldoktor@redhat.com>