Fix attach exit on darwin

Docker-DCO-1.1-Signed-off-by: Guillaume J. Charmes <guillaume@charmes.net> (github: creack)
improve deprecation message

Docker-DCO-1.1-Signed-off-by: Victor Vieux <victor.vieux@docker.com> (github: vieux)
Merge pull request #4603 from creack/fix_osx_attach

Fix OSX attach exit issue
Merge pull request #4604 from vieux/improve_deprecation_warning_flags

improve deprecation message