Resync charm-helpers to pickup the latest code for calculation
of worker process configuration, creating better default
worker configuration when deploying in LXD containers.
Switch the skew between public and admin processes to favour
public 0.75/0.25 as the public API endpoints of a service will
typically get a larger number of hits.
Fixup unit test for minor behavioural change in charm-helpers.
Change-Id: I4ab1d28f907ce29d5602b48ba7a438fc3690277c
Closes-Bug: 1665270
Closes-Bug: 1686049
21a4e5beb1