MINOR: server: srv_append_status refacto

MINOR: server: srv_append_status refacto

srv_append_status() has become a swiss-knife function over time.
It is used from server code and also from checks code, with various
inputs and distincts code paths, making it very hard to guess the
actual behavior of the function (resulting string output).

To simplify the logic behind it, we're dividing it in multiple contextual
functions that take simple inputs and do explicit things, making them
more predictable and easier to maintain.