Until now, it has been the responsibility of an individual daemon to call
die_if_already_running() at an appropriate time. A long time ago, this
had to happen *before* daemonizing, because once the process daemonized
itself there was no way to report failure to the process that originally
started the daemon. With the introduction of daemonize_start(), this is
now possible, but we haven't been taking advantage of it.
Therefore, this commit integrates the die_if_already_running() call into
daemonize_start() and deletes the calls to it from individual daemons.
These initial bindings pass a few hundred of the corresponding tests
for C implementations of various bits of the Open vSwitch library API.
The poorest part of them is actually the Python IDL interface in
ovs.db.idl, which has not received enough attention yet. It appears
to work, but it doesn't yet support writes (transactions) and it is
difficult to use. I hope to improve it as it becomes clear what
semantics Python applications actually want from an IDL.
