[charts/redis-ha] Readonly filesystem and Probes

[sindrip]

What this PR does / why we need it:

This adds a securityContext on each container with a configuration option for readOnlyRootFilesystem defaulted to false.

This also adds readiness and liveness probes for the split-brain-fix container. The probes are defaulted to off.

Which issue this PR fixes

(optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged)

• fixes #

Special notes for your reviewer:

Checklist

[Place an '[x]' (no spaces) in all applicable fields. Please remove unrelated fields.]

• [x] DCO signed
• [x] Chart Version bumped
• [x] Variables are documented in the README.md
• [x] Title of the PR starts with chart name (e.g. [stable/mychartname])

[DandyDeveloper]

@sindrip Sorry, I wasn't notified via email about this :( I'll check and test over the coming next couple of days.

[sindrip]

Hi, don't worry about it, I just assumed you were busy with other things. Thank you!

[haljin]

Hi, any progress on this? We could use that change as well

[sindrip]

I saw that some conflicts had been introduced from a merge that I have resolved now.

@DandyDeveloper do you have time to look at this?

[DandyDeveloper]

@sindrip I do, I will be checking shortly. I can't believe this has been open so long, sorry.

[sindrip]

Hi @DandyDeveloper, no worries. Is there anything you want me to do to enable this, or are you planning to take care of these new conflicts?