Merge branch 'feature/docker-hub-google-mirror' into 'master'

install-docker.sh: use registry mirror mirror.gcr.io

See merge request !1
1 job for master in 36 seconds (queued for 3 seconds)
Name Stage Failure
failed
shellcheck Lint There has been a runner system failure, please try again
Using Docker executor with image koalaman/shellcheck-alpine:stable ...
Pulling docker image koalaman/shellcheck-alpine:stable ...
ERROR: Preparation failed: Error response from daemon: toomanyrequests: You have reached your pull rate limit. You may increase the limit by authenticating and upgrading: https://www.docker.com/increase-rate-limit (docker.go:142:1s)
Will be retried in 3s ...
Using Docker executor with image koalaman/shellcheck-alpine:stable ...
Pulling docker image koalaman/shellcheck-alpine:stable ...
ERROR: Preparation failed: Error response from daemon: toomanyrequests: You have reached your pull rate limit. You may increase the limit by authenticating and upgrading: https://www.docker.com/increase-rate-limit (docker.go:142:1s)
Will be retried in 3s ...
ERROR: Job failed (system failure): Error response from daemon: toomanyrequests: You have reached your pull rate limit. You may increase the limit by authenticating and upgrading: https://www.docker.com/increase-rate-limit (docker.go:142:1s)