Update the readiness/liveness Probes configuration.

[ishan16696]

What this PR does / why we need it:

1. Adds failureThreshold to 5 for both readiness and liveness Probe.
2. Update the livenessProbe for etcd making the consistency serializable using --consistency="s"

Which issue(s) this PR fixes:
Fixes #280 partially as there is still a room for improvement(more info)

Special notes for your reviewer:
For values of initialDelaySeconds and failureThreshold can be discussed. I'm open for change.
cc @timuthy

Release note:

livenessProbe of etcd container has been updated to `ETCDCTL_API=3 etcdctl get foo --consistency=s` making the consistency `serializable`. 

failureThreshold has been updated to `5` for both livenessProbe and readinessProbe of etcd.

[ishan16696]

Should we include this PR as well in our upcoming release of druid ?

cc @abdasgupta @timuthy @aaronfern

[timuthy]

Thanks for the PR @ishan16696. Please also add a release note so that users are aware of the change.

[ishan16696]

Added the release note. PTAL @timuthy

[timuthy]

/lgtm