improve docker layers using COPY --chown

[cyriltovena]

Closes #481

After following suggestions, I'm having:

gcr.io/agones-images/agones-ping              0.8.0-9646141     18.9MB
gcr.io/agones-images/agones-sdk               0.8.0-9646141      42.7MB
gcr.io/agones-images/agones-controller        0.8.0-9646141    44.5MB

compared to previously:

gcr.io/agones-images/agones-ping              0.7.0-f3cb1ee  31.6MB
gcr.io/agones-images/agones-sdk               0.7.0-f3cb1ee   78.9MB
gcr.io/agones-images/agones-controller        0.7.0-f3cb1ee 82.5MB

@Oleksii-Terekhov @aLekSer Good catch guys !

[agones-bot]

Build Succeeded 👏

Build Id: fb4478e0-d3df-4418-b010-89c5ba879730

The following development artifacts have been built, and will exist for the next 30 days:

• image: gcr.io/agones-images/agones-controller:0.8.0-dc48f9e
• image: gcr.io/agones-images/agones-sdk:0.8.0-dc48f9e
• image: gcr.io/agones-images/agones-ping:0.8.0-dc48f9e
• Linux C++ SDK (build: dev): agonessdk-0.8.0-dc48f9e-dev-linux-arch_64.tar.gz
• Linux C++ SDK (build: runtime): agonessdk-0.8.0-dc48f9e-runtime-linux-arch_64.tar.gz
• Linux C++ SDK (source): agonessdk-0.8.0-dc48f9e-src.zip
• SDK Server: agonessdk-server-0.8.0-dc48f9e.zip

To install this version:

• git fetch https://github.com/GoogleCloudPlatform/agones.git pull/482/head:pr_482 && git checkout pr_482
• helm install install/helm/agones --namespace agones-system --name agones --set agones.image.tag=0.8.0-dc48f9e

[markmandel]

LGTM!