Fixed jobs count for current shell

The jobs_segment had a major bug. It was always showing me 0 jobs!

It was checking for processes with PPID same as the Python script's PPID.
But actually their grand-parents would be same:

  We generate the entire prompt by evaluating the python script
  in a $() which creates a separate sub-process which is the parent of
  the Python process. The original shell is the parent of the $()
  sub-process. So, we need to get the grand parent id.