daemon: decouple init logic from main loop

main() func contained both initialization and main loop logic.
This made certain operations like restarting problematic and
required dirty hacks in form of goto jumps.

This commit moves the main loop logic into daemon_eventloop(),
cleans up main, and makes restart logic clear: daemon_mainloop()
is run in a loop with a restart condition checked at the end.

Reviewed by: kevans
Pull Request: https://github.com/freebsd/freebsd-src/pull/699