qdevice: Propagate error to exit code

qdevice: Propagate error to exit code

Net model never returned error when qdevice_model_run was called. This
was incorrect because with exception of local ipc close all other
disconnect reasons are errors.

Solution is to return proper error code.

Also instead of exit right after qdevice_model_run it's better to store
result value, try clean resources and use stored value to return correct
exit code.

Signed-off-by: Jan Friesse <jfriesse@redhat.com>