Make it easier to parse the output consistently:

Always make "* top %f TEST ${test} starting" the first message.

Tag vtest and varnishtest message with "VTEST" instead of "TEST"

bin/varnishtest/vtc.c

@@ -503,6 +503,8 @@ exec_file(const char *fn, const char *script, const char *tmpdir,
 	vltop = vtc_logopen("top");
 	AN(vltop);
 
+	vtc_log(vltop, 1, "TEST %s starting", fn);
+
 	init_macro();
 	init_server();
 	init_syslog();
@@ -537,7 +539,6 @@ exec_file(const char *fn, const char *script, const char *tmpdir,
 	AZ(fclose(f));
 
 	vtc_stop = 0;
-	vtc_log(vltop, 1, "TEST %s starting", fn);
 
 	vtc_thread = pthread_self();
 	parse_string(script, cmds, NULL, vltop);

bin/varnishtest/vtc_misc.c

@@ -74,7 +74,7 @@ cmd_vtest(CMD_ARGS)
 		return;
 	AZ(strcmp(av[0], "vtest"));
 
-	vtc_log(vl, 1, "TEST %s", av[1]);
+	vtc_log(vl, 1, "VTEST %s", av[1]);
 	AZ(av[2]);
 }
 
@@ -96,7 +96,7 @@ cmd_varnishtest(CMD_ARGS)
 		return;
 	AZ(strcmp(av[0], "varnishtest"));
 
-	vtc_log(vl, 1, "TEST %s", av[1]);
+	vtc_log(vl, 1, "VTEST %s", av[1]);
 	AZ(av[2]);
 }