split the container 'saltmaster' into a separate 'saltapi' and true 'saltmaster'

[erwindon]

Is your feature request related to a problem? Please describe.
The container runs 2 programs.
This is bad practice and needs an extra program "supervisor"

Describe the solution you'd like
Split the container in 2 parts. one for salt-api, and one for (onlt) salt-master.

Additional context
I realised that this is needed while reviewing PR #743

[erwindon]

easier said than done.
salt-api depends on salt-master and basically needs to be on the same host (same IP-number or even same unix-socket)
let's see whether this is still doable...

[erwindon]

there is no easy solution.
so the cure is worse than the problem