tests: Fix enumeration value

Commit 3a773c43 introduced the testCompareNetXML2XMLResult
enumeration; however, in one instance the result variable was
assigned a value from the very similar testCompareDocXML2XMLResult
enumeration, leading to a build error.

  networkxml2xmltest.c:33:42: error:
    implicit conversion from enumeration type 'testCompareDomXML2XMLResult'
    to different enumeration type 'testCompareNetXML2XMLResult'
    [-Werror,-Wenum-conversion]

  testCompareNetXML2XMLResult result = TEST_COMPARE_DOM_XML2XML_RESULT_SUCCESS;
                              ~~~~~~   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Use the proper value (TEST_COMPARE_NET_XML2XML_RESULT_SUCCESS) instead.

tests/networkxml2xmltest.c

@@ -30,7 +30,7 @@ testCompareXMLToXMLFiles(const char *inxml, const char *outxml,
 {
     char *actual = NULL;
     int ret;
-    testCompareNetXML2XMLResult result = TEST_COMPARE_DOM_XML2XML_RESULT_SUCCESS;
+    testCompareNetXML2XMLResult result = TEST_COMPARE_NET_XML2XML_RESULT_SUCCESS;
     virNetworkDefPtr dev = NULL;
 
     if (!(dev = virNetworkDefParseFile(inxml))) {