net tests: fix api.addNetwork call

commit 7b39590d4 forgot to rename the function in this test.

Change-Id: Ia2cbb18a4abaf58362db17beb00f00b6cf5e9db0
Signed-off-by: Dan Kenigsberg <danken@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/36125
Reviewed-by: Petr Horáček <phoracek@redhat.com>
Tested-by: Petr Horáček <phoracek@redhat.com>