DATAMONGO-1971 - Install MongoDB 3.7.9 on TravisCI.

We now download and unpack MongoDB directly instead of using TravisCI's outdated MongoDB version.

Original pull request: #554.

.travis.yml

@@ -3,44 +3,34 @@ language: java
 jdk:
   - oraclejdk8
 
-before_script:
-  - mongod --version
+before_install:
+  - mkdir -p downloads
+  - mkdir -p var/db var/log
+  - if [[ ! -d downloads/mongodb-linux-x86_64-ubuntu1604-${MONGO_VERSION} ]] ; then cd downloads && wget https://fastdl.mongodb.org/linux/mongodb-linux-x86_64-ubuntu1604-${MONGO_VERSION}.tgz && tar xzf mongodb-linux-x86_64-ubuntu1604-${MONGO_VERSION}.tgz && cd ..; fi
+  - downloads/mongodb-linux-x86_64-ubuntu1604-${MONGO_VERSION}/bin/mongod --version
+  - downloads/mongodb-linux-x86_64-ubuntu1604-${MONGO_VERSION}/bin/mongod --dbpath var/db --replSet rs0 --fork --logpath var/log/mongod.log
+  - sleep 10
   - |-
-    echo "replication:
-      replSetName: rs0" | sudo tee -a /etc/mongod.conf
-  - sudo service mongod restart
-  - sleep 20
-  - |-
-    mongo --eval "rs.initiate({_id: 'rs0', members:[{_id: 0, host: '127.0.0.1:27017'}]});"
-  - sleep 15
-
-services:
-  - mongodb
-
+    downloads/mongodb-linux-x86_64-ubuntu1604-${MONGO_VERSION}/bin/mongo --eval "rs.initiate({_id: 'rs0', members:[{_id: 0, host: '127.0.0.1:27017'}]});"
+    sleep 15
+    
 env:
   matrix:
     - PROFILE=ci
     - PROFILE=mongo36-next
+  global:
+    - MONGO_VERSION=3.7.9
 
-# Current MongoDB version is 2.4.2 as of 2016-04, see https://github.com/travis-ci/travis-ci/issues/3694
-# apt-get starts a MongoDB instance so it's not started using before_script
 addons:
   apt:
-    sources:
-      - mongodb-3.4-precise
     packages:
-    - mongodb-org-server
-    - mongodb-org-shell
-    - oracle-java8-installer
+      - oracle-java8-installer
 
 sudo: false
 
 cache:
   directories:
     - $HOME/.m2
-
-install:
-  - |-
-    mongo admin --eval  "db.adminCommand({setFeatureCompatibilityVersion: '3.4'});"
+    - downloads
 
 script: "mvn clean dependency:list test -P${PROFILE} -Dsort"