Go script makes it easy to read/maintain. Also updated the timeout
in Dockerfiles from 5s to default 30s and test interval to 1m
Higher timeout makes sense as server may sometimes respond slowly
if under high load as reported in #6974Fixes#6974
This PR simplifies the process of developer build of local
docker containers using `make docker`.
You need to provide a TAG i.e
```
TAG=y4m4/minio:exp make docker
```
This PR allows 'minio update' to not only shows update banner
but also allows for in-place upgrades.
Updates are done safely by validating the downloaded
sha256 of the binary.
Fixes#4781
