When sender_t is used to send ESP packets this would otherwise cause an extreme
amount of debug messages.
With this change all messages sent via sender_t.send_no_marker() cause no extra
DBG1 log message, but for debugging purposes the socket plugins do log the same
message again with DBG2 for all packets.
This ensures that no threads are active when plugins and the rest of the
daemon are unloaded.
callback_job_t was simplified a lot in the process as its main
functionality is now contained in processor_t. The parent-child
relationships were abandoned as these were only needed to simplify job
cancellation.
Tobias Brunner