qemu.py: Call logging.basicConfig() automatically

qemu.py: Call logging.basicConfig() automatically

Not all scripts using qemu.py configure the Python logging
module, and end up generating a "No handlers could be found for
logger" message instead of actual log messages.

To avoid requiring every script using qemu.py to configure
logging manually, call basicConfig() when creating a QEMUMachine
object.  This won't affect scripts that already set up logging,
but will ensure that scripts that don't configure logging keep
working.

Reported-by: Kevin Wolf <kwolf@redhat.com>
Fixes: 4738b0a85a0c2031fddc71b51cccebce0c4ba6b1
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Message-Id: <20170921162234.847-1-ehabkost@redhat.com>
Reviewed-by: Cleber Rosa <crosa@redhat.com>
Acked-by: Lukáš Doktor <ldoktor@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>