a single command string to run, and an inner function (run_command) that
runs that single string.
Move the list of start/stop commands to run from a switch statement into
an array, with a new placeholder parameter IP__OP for actually creating
or removing the jail.
When jail creation fails, revert all non-exec commands in reverse order.
Make the parallelism limit a global instead of always passing it
to run_command and finish_command.
In the case of an empty command string, try to run any other strings
the command may have.
Replace JF_BACKGROUND with its sort-of opposite JF_SLEEPQ.
Change j->comstring earlier to render JF_RUNQ unncessary.
Change the if-else series to a more readable switch statement.
Treat IP_STOP_TIMEOUT like a command, calling run_command which then
calls term_procs.
When the IP_STOP_TIMEOUT "command" finishes, it shouldn't mess with
the parallelism limit.
Make sufficient checks in finish_command and run_command so that
the nonintuitive j->comstring null check isn't necessary to run them.
Rename the "waiting" queue to "depend", because the "sleeping" and
"runnable" queues are also used to wait for something.
path must be absolute.
mount paths must exist and have no symlinks beyond the jail's path itself.
consolelog must exist (apart from the final component) and have no
symlinks beyond the jail's path itself.
