run: Avoid machine_type setting when using custom config

When custom config was used and default_guest_os was None,
the _process_machine_type added a DEFAULT_MACHINE_TYPE filter,
which might fail on configs without 'i440fx' variant.

Signed-off-by: Lukáš Doktor <ldoktor@redhat.com>
virt: Adds migration tests for dst problem.

1) Migration to read-only space.
2) Migration to low space destination.

Both migration uses exec protocol for migration to file.

qemu-kvm is started like Expect class not only like Tail.

Signed-off-by: Jiří Župka <jzupka@redhat.com>
virttest.bootstrap: Don't change a list when transversing it

Currently, when creating config files, autotest tries to find out
the config files that need to be overridden in testdir/cfg/*.cfg.

But it tries to pop the element for the list during traversing
itself, this is very dangerous, and it might cause an error when
running get_started.py, because the list wasn't updated yet, but
the transverse index wasn't updated.

Signed-off-by: Mike Qiu <qiudayu@linux.vnet.ibm.com>
virttest.qemu_installer: Autodetect qemu based on host arch

When detecting appropriate qemu names by default to run the
test suite, right now x86_64 is assumed. So, in order to
support other host architectures, such as ppc64, guess the
appropriate qemu name based on the host architecture.

Signed-off-by: Mike Qiu <qiudayu@linux.vnet.ibm.com>