Remove incorrect SIGKILL handler.

As per POSIX signal handling SIGKILL does not work.

Fixes #2928
Merge pull request #2929 from pnasrat/2928-fix-signal-handling

Remove incorrect SIGKILL handler.
Merge pull request #2952 from codeaholics/2126-registry-close-wait

Closing HTTP connection after Registry ping
Merge remote-tracking branch 'docker/master' into dev