Explicitly set malloc storage in the regression test for #2530.

Storage defaults to umem where libumem is available, as is usually
the case on SunOS. So checking SMA.* stats was causing the test to
fail on Solaris.

bin/varnishtest/tests/r02530.vtc

@@ -30,7 +30,7 @@ server s1 {
 	sendhex 1f8b
 } -start
 
-varnish v1 -vcl+backend {
+varnish v1 -arg "-smalloc -sTransient=malloc" -vcl+backend {
 	sub vcl_recv {
 		if (req.url == "/pass") {
 			return (pass);