integration: lower timeout for stop/restart tests

Docker-DCO-1.1-Signed-off-by: Cristian Staretu <cristian.staretu@gmail.com> (github: unclejack)
Merge pull request #8192 from unclejack/lower_timeout_integ

integration: lower timeout for stop/restart tests
Merge branch 'master' of github.com:docker/docker into ipv6