[build] upgrade docker in travis using addons (#4481)

* [build] upgrade docker in travis using addons
* [build] upgrade docker in travis with debug command
* [build] retrying addons
* [build] debug log
* [build] clean debug log

Author: sophoah

Diff for: .travis.yml

@@ -13,12 +13,13 @@ env:
   - TEST="bash ./scripts/travis_rpc_checker.sh"
   - TEST="bash ./scripts/travis_rosetta_checker.sh"
 
-before_install:
-  # upgrade docker to the latest supported by the OS loaded in the travis image
-  - curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -
-  - sudo add-apt-repository --yes "deb [arch=amd64] https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable"
-  - sudo apt-get update
-  - sudo apt-get -y -o Dpkg::Options::="--force-confnew" install docker-ce
+# upgrade docker to latest stable version
+addons:
+  apt:
+    sources:
+      - sourceline: deb https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable
+    packages:
+    - docker.io
 
 install:
   # default working directory with source code is automatically set to