Allow JM to have more than 1 replicas

[jto]

In a HA setup, one may want to have more than 1 JM replica.
fixes #256

[martinbomio]

@jto do you know if this has any implications? What happens in setups where there's no HA?

[jto]

@martinbomio I'll need to test it on our dev cluster.

[jto]

Thinking about it I think the service will load balance between the JMs which is probably a terrible thing to do.
Maybe HA should be supported by the operator directly (as in high-availability: true) and not something you set up "manually". At the same time, if you explicitly ask for the JM to have more than 1 replica, maybe you know what you're doing.

@regadas wdyt ?

[regadas]

Hm, right... maybe we could just add the required props for HA automatically when setting replicas >1? keeping the default value as 1 and then be clear of the behavior in docs. wdyt?

[jto]

@regadas Yep that's what I was thinking too.

[martinbomio]

@jto @regadas do we have an issue to track this festure request? If we don't, I can create one given this is still relevant

[regadas]

I think this one is a bit related #256. But feel free to open a new one if you feel it doesn't capture it all.