zsh/coredumpctl: Fix the completion

zsh/coredumpctl: Fix the completion

An output from coredumpctl list is like

> TIME                            PID   UID   GID SIG COREFILE  EXE
> Sun 2016-05-29 18:44:03 CEST  14578  1000  1000   6 none      /tmp/pacaurtmp-wieland/python33/src/Python-3.3.6/python

  ^1  ^2         ^3       ^4    ^5

, but the previous sub() command turns that into

> TIMEPID   UID   GID SIG COREFILE  EXE
> Sun2016-05-29 18:44:03 CEST  14578  1000  1000   6 none      /tmp/pacaurtmp-wieland/python33/src/Python-3.3.6/python
  ^1            ^2       ^3    ^4     ^5

so the whole pipeline generated entries like

$UID:$DESCRIPTION

but that's not useful and probably not what was supposed to happen.

This now generates entries like

$PID:$DESCRIPTION

which make everything work.

Note that with this commmit, the completions will be sorted by PID by
ZSH.