Add package in Dockerfile for bash

[Ryner51]

I noticed that the Dockerfile in docker/operator pulls from alpine:3.8.

It would be nice to add the ability to execute bash on the pod to verify that any configuration files are being deployed correctly.

Example command:
kubectl exec -ti /bin/bash

Output:
kubectl exec -ti /bin/bash
OCI runtime exec failed: exec failed: container_linux.go:348: starting container process caused "exec: "/bin/bash": stat /bin/bash: no such file or directory": unknown

Docker File Enhancement:
RUN apk add --no-cache bash

[fahlke]

I would suggest to not extend the container image with unnecessary stuff (e.g. Bash).

Either use ephemeral/debug containers when you have the alpha feature gate (EphemeralContainers) activated in Kubernetes 1.18+ or simply use /bin/ash or /bin/sh with kubernetes exec in Alpine container images.

kubectl exec -ti ${POD_NAME} -- /bin/ash