optimize travis ci job

.travis.yml

@@ -24,18 +24,7 @@ env:
     - PHP_VERSION=71 BUILD_SERVICE=php-worker
     - PHP_VERSION=72 BUILD_SERVICE=php-worker
 
-    - PHP_VERSION=56 BUILD_SERVICE=mssql
-    - PHP_VERSION=70 BUILD_SERVICE=mssql
-    - PHP_VERSION=71 BUILD_SERVICE=mssql
-
-    - PHP_VERSION=56 BUILD_SERVICE=rethinkdb
-    - PHP_VERSION=70 BUILD_SERVICE=rethinkdb
-    - PHP_VERSION=71 BUILD_SERVICE=rethinkdb
-
-    - PHP_VERSION=56 BUILD_SERVICE=aerospike
-    - PHP_VERSION=70 BUILD_SERVICE=aerospike
-    - PHP_VERSION=71 BUILD_SERVICE=aerospike
-
+    - PHP_VERSION=NA BUILD_SERVICE="mssql rethinkdb aerospike"
     - PHP_VERSION=NA BUILD_SERVICE="applications blackfire minio percona nginx caddy apache2 mysql mariadb postgres postgres-postgis neo4j mongo redis"
     - PHP_VERSION=NA BUILD_SERVICE="adminer phpmyadmin pgadmin"
     - PHP_VERSION=NA BUILD_SERVICE="memcached beanstalkd beanstalkd-console rabbitmq elasticsearch certbot mailhog maildev selenium jenkins proxy proxy2 haproxy"