ptest-runner: enable child procs as session leader
When running the run-execscript bash ptest as a user rather than root, a warning:
bash: cannot set terminal process group (16036): Inappropriate ioctl for device
bash: no job control in this shell
contaminates the bash log files causing the test to fail. This happens only
when run under ptest-runner and not when interactively testing!
The changes made to fix this include:
1. Get the process group id (pgid) before forking,
2. Set the pgid in both the parent and child to avoid a race,
3. Find, open and set permission on the child tty, and
4. Allow the child to attach to controlling tty.
Signed-off-by: Randy MacLeod <Randy.MacLeod@windriver.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
