stats send updates. not many people using this but the changes here are internal

The key issued fixed here is a possible race where a source could get started between the
stats being generated and the client being added.  now we register the client, so that stats
for new details are added as normal, but the client itself is inactive (therefore no sending)
until the full list is made, and prepended. only then is the client made active. adn woken up

we also avoid the explicit wakeup, it's not required and a manual wakeup on exit is triggered.
This will be more useful later with relays switching masters.
internal name cleanup for consistency.

The idea here is we use the term 'host' inside a relay block, not 'master' like before (although
master is still accepted).  Much of this commit deals with the internal renaming so no actual
usage will differ.
need to clear this setting on relay cleanup.

cannot rely on stat details being still allocated later during the relay
release.