Add a "wait-running" primitive to varnish instances, so we can

avoid fixed sleeps waiting for the child process to start.

bin/varnishtest/tests/v00010.vtc

@@ -5,6 +5,8 @@ server s1 {
 	txresp -hdr "Foo: bar" -body "abcdef\n"
 	rxreq
 	txresp -hdr "Panic: please" -body "012345\n"
+	close
+
 	sema r1 sync 2
 	accept
 	rxreq
@@ -33,10 +35,10 @@ client c1 {
 	rxresp
 	txreq -url "/foo"
 	# Don't expect answer, the server crashed.
-	sema r1 sync 2
 } -run
 
-delay 2.5
+varnish v1 -wait-running
+sema r1 sync 2
 
 client c1 {
 	txreq -url "/"

bin/varnishtest/vtc_varnish.c

@@ -119,6 +119,30 @@ varnish_ask_cli(const struct varnish *v, const char *cmd, char **repl)
 	return ((enum VCLI_status_e)retval);
 }
 
+/**********************************************************************
+ *
+ */
+
+static void
+wait_running(const struct varnish *v)
+{
+	char *r;
+	enum VCLI_status_e st;
+
+	while (1) {
+		st = varnish_ask_cli(v, "status", &r);
+		if (st != CLIS_OK)
+			vtc_log(v->vl, 0,
+			    "CLI status command failed: %u %s", st, r);
+		if (!strcmp(r, "Child in state running")) {
+			free(r);
+			break;
+		}
+		free(r);
+		(void)usleep(200000);
+	}
+}
+
 /**********************************************************************
  * Varnishlog gatherer + thread
  */
@@ -431,6 +455,7 @@ varnish_start(struct varnish *v)
 		return;
 	if (u != CLIS_OK)
 		vtc_log(v->vl, 0, "CLI start command failed: %u %s", u, resp);
+	wait_running(v);
 	free(resp);
 	u = varnish_ask_cli(v, "debug.xid 1000", &resp);
 	if (vtc_error)
@@ -815,6 +840,10 @@ cmd_varnish(CMD_ARGS)
 			varnish_stop(v);
 			continue;
 		}
+		if (!strcmp(*av, "-wait-running")) {
+			wait_running(v);
+			continue;
+		}
 		if (!strcmp(*av, "-wait")) {
 			varnish_wait(v);
 			continue;