* MM-14145: The config store Set will now Save automatically
When UpdateConfig (and configStore.Set) is called in admin.go and
config.go, commonStore.Set now takes a store-specific persist function.
It uses that persist function to save the configuration automatically.
Removed: Now callers do not have to call configStore.Save or
app.PersistConfig, and those functions have been removed.
Possible downside: this means a "failed to persist config" error can now
be thrown during a app.UpdateConfig or commonStore.Set call. But
considering application code never really sets a config without saving
it (except in the test cases, which were testing that -- see below), it
seems fine to group these responsibilities.
Also removed: tests for 'set without save'. Since that can not happen
anymore, the tests are not needed.
* Removed Save completely, cleaned up formatting, joined save test with
set tests.
* fixed shadowed variable error
8bd182c38f