torture: Clarify refusal to run more than one torture test

This commit clarifies error messages -- you only get to run one torture
test at a time!
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

kernel/torture.c

@@ -602,8 +602,9 @@ bool torture_init_begin(char *ttype, bool v, int *runnable)
 {
 	mutex_lock(&fullstop_mutex);
 	if (torture_type != NULL) {
-		pr_alert("torture_init_begin: refusing %s init: %s running",
+		pr_alert("torture_init_begin: Refusing %s init: %s running.\n",
 			 ttype, torture_type);
+		pr_alert("torture_init_begin: One torture test at a time!\n");
 		mutex_unlock(&fullstop_mutex);
 		return false;
 	}