mosquitto_passwd returns 1 on an error condition

When attempting to update a user that does not exist.

Closes #1414. Thanks to kdgde.

ChangeLog.txt

@@ -4,6 +4,8 @@
 Broker:
 - Restrict topic hierarchy to 200 levels to prevent possible stack overflow.
   Closes #1412.
+- mosquitto_passwd now returns 1 when attempting to update a user that does
+  not exist. Closes #1414.
 
 
 1.6.5 - 20190912

src/mosquitto_passwd.c

@@ -223,6 +223,7 @@ int delete_pwuser(FILE *fptr, FILE *ftmp, const char *username)
 	}
 	if(!found){
 		fprintf(stderr, "Warning: User %s not found in password file.\n", username);
+		return 1;
 	}
 	return 0;
 }