Cleanup monitoring in puppet-tails

The code for monitoring was written without taking masterless nodes into account. Currently, monitoring for stone is crudely hacked in place, but the codebase should really be redesigned to accomodate masterless nodes more neatly.

Parent Task: #16958

Related issues

Related to #16215 (closed)
Blocks #13284

Original created by @groente on 16934 (Redmine)

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