Add download localhost and enable for CI

* Add download_localhost for the download_run_once mode, which is
  use the ansible host (a travis node for CI case) to store and
  distribute containers across cluster nodes in inventory.
  Defaults to false.
* Rework download_run_once logic to fix idempotency of uploading
  containers.
* For Travis CI, enable docker images caching and run Travis
  workers with sudo enabled as a dependency
* For Travis CI, deploy with download_localhost and download_run_once
  enabled to shourten dev path drastically.
* Add compression for saved container images. Defaults to 'best'.

Signed-off-by: Bogdan Dobrelya <bdobrelia@mirantis.com>
Co-authored-by: Aleksandr Didenko <adidenko@mirantis.com>

.travis.yml

@@ -1,4 +1,7 @@
-sudo: false
+sudo: required
+
+services:
+  - docker
 
 git:
   depth: 5
@@ -6,6 +9,7 @@ git:
 env:
   global:
     GCE_USER=travis
+    LOG_LEVEL=-v
     SSH_USER=$GCE_USER
     TEST_ID=$TRAVIS_JOB_NUMBER
     CONTAINER_ENGINE=docker
@@ -114,6 +118,8 @@ before_install:
   # W/A https://github.com/ansible/ansible-modules-core/issues/5196#issuecomment-253766186
   - pip install --user apache-libcloud==0.20.1
   - pip install --user boto==2.9.0 -U
+  # Load cached docker images
+  - if [ -d /var/tmp/releases ]; then find /var/tmp/releases -type f -name "*.tar" | xargs -I {} sh -c "zcat {} | docker load"; fi
 
 cache:
   - directories:
@@ -153,6 +159,7 @@ script:
     -e bootstrap_os=${BOOTSTRAP_OS}
     -e ansible_python_interpreter=${PYPATH}
     -e download_run_once=true
+    -e download_localhost=true
     -e local_release_dir=/var/tmp/releases
     cluster.yml