virdbustest: Don't leak @out_strv1

In testMessageSingleArrayRef the string is doubly referenced.
Therefore we have to free also the first pointer to the string.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>

tests/virdbustest.c

@@ -323,6 +323,7 @@ static int testMessageSingleArrayRef(const void *args ATTRIBUTE_UNUSED)
  cleanup:
     if (out_strv1)
         VIR_FREE(out_strv1[0]);
+    VIR_FREE(out_strv1);
     virDBusMessageUnref(msg);
     return ret;
 }