tests: fix running of qemuxml2argvtest program

The previous commit:

  commit a455d41e
  Author: Daniel P. Berrangé <berrange@redhat.com>
  Date:   Thu Jan 25 09:35:50 2018 +0000

    conf: expand network device callbacks to cover resolving NIC type

mistakenly dropped qemuxml2argvtest from the tests due to a typo.
Signed-off-by: NDaniel P. Berrangé <berrange@redhat.com>

tests/Makefile.am

@@ -291,7 +291,7 @@ test_programs += qemuxml2xmltest \
 if WITH_NETWORK
 # Dep on the network driver callback for resolving NIC
 # actual type. XXX remove this dep.
-test_programs += qemuxml2xmltest
+test_programs += qemuxml2argvtest
 endif WITH_NETWORK
 test_helpers += qemucapsprobe
 test_libraries += libqemumonitortestutils.la \