qga: do not override configuration verbosity

Move the default verbosity settings before loading the configuration
file, or it will overwrite it. Found thanks to writing qga tests :)

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
