Revert "varlink: initialize Varlink with 0"

This reverts commit 8688c29b5a, but leaves the
reproducer. Structured assignment should be enough to fully initialize the
variable and new0 is not necessary.

src/shared/varlink.c

@@ -246,8 +246,7 @@ static int varlink_new(Varlink **ret) {
 
         assert(ret);
 
-        /* Here use new0 as the below structured initializer is nested. */
-        v = new0(Varlink, 1);
+        v = new(Varlink, 1);
         if (!v)
                 return -ENOMEM;