Use __DECONST (instead of my own attempted re-invention) for the iov
parameters to jail_get/set(2). Similarly remove the decost-ish hack
from execvp's argv, except the __DECONST is only added at very end.
While I'm at it, remove an unused variable and fix a comment typo.
Some errors printed the jail name for unnamed (command line) jails.
Attempting to create an already-existing jail from the command line
returned with no error (even for non-root) due to bad logic in
start_state.
Ignore kvm_proc errors, which are typically caused by permission
problems. Instead, stop ignoring permission errors when removing
a jail (but continue to silently ignore other errors, i.e. the
jail no longer existing). This makes non-root attempts at removing
a jail give a clearer error message.
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.
