executable file even if the specified action/filename does not
contain a '/' character; convert execv() to execvp().
Submitted by: Christian S.J. Peron <maneo@bsdpro.com>
PR: bin/54109
o Add jexec(8) to execute a command in an existing jail.
o Add -j option for killall(1) to kill all processes in a specified
jail.
o Add -i option to jail(8) to output jail ID of newly created jail.