Cygwin: console: Re-fix open() failure on exec() by console owner

Cygwin: console: Re-fix open() failure on exec() by console owner

Previous fix (commit df0953aa298c) fixes only a part of the problem.
Since exec() overrides the cygwin pid of the caller process, it makes
console owner handling complex. This patch makes console use Windows
pid as the owner pid (con.owner) instead of cygwin pid to make the
handling simpler.

Fixes: df0953aa298c ("Cygwin: console: Fix open() failure when the console owner calls exec().")
Signed-off-by: Takashi Yano <takashi.yano@nifty.ne.jp>