tests: initialize some variables

Found by cppcheck:
[tests/metadatatest.c:284]: (error) Uninitialized variable: test
[tests/objecteventtest.c:855]: (error) Uninitialized variable: test

Signed-off-by: Ján Tomko <jtomko@redhat.com>
Reviewed-by: Jiri Denemark <jdenemar@redhat.com>

tests/metadatatest.c

@@ -268,7 +268,7 @@ testTextMetadata(const void *data)
 static int
 mymain(void)
 {
-    struct metadataTest test;
+    struct metadataTest test = { 0 };
     int ret = EXIT_SUCCESS;
 
     if (!(test.conn = virConnectOpen("test:///default")))

tests/objecteventtest.c

@@ -835,7 +835,7 @@ timeout(int id ATTRIBUTE_UNUSED, void *opaque ATTRIBUTE_UNUSED)
 static int
 mymain(void)
 {
-    objecteventTest test;
+    objecteventTest test = { 0 };
     int ret = EXIT_SUCCESS;
     int timer;