This patch removes the now heavily outdated (and non-working) support
for callback plugins. I.e. plugins that attach themselves to services
listed in /etc/finit.conf and can be queried to determine if a service
should be started or stopped.
The Finit3 support for adding/removing services at runtime with plain
text *.conf files in /etc/finit.d and `initctl reload`, this old, and
rather cumbersome service callback feature, is not longer supported.
Signed-off-by: Joachim Nilsson <troglobit@gmail.com>