another attempted travis fix for mysql issues

.travis.yml

@@ -7,5 +7,5 @@ services:
 script:
   - npm test
 before_install:
-  - docker pull mysql:latest
+  - docker pull mariadb:latest
   - docker images

test/docker-compose-testbed.yaml

@@ -9,7 +9,7 @@ networks:
 
 services:
   mysql:
-    image: mysql:latest
+    image: mariadb:latest
     environment: 
       MYSQL_RANDOM_ROOT_PASSWORD: "yes"
       MYSQL_DATABASE: jambones