Remove incorrect SIGKILL handler.

As per POSIX signal handling SIGKILL does not work.

Fixes #2928
Make race condition more obvious by performing more asserts
Make CopyEscapable consistent with Copy and return `nil` in case of success instead of io.EOF
Closing connection after ping
Make sure the container is running before testing against it (TestAttachDetach)
Add a GetPtyMaster() method to container to retrieve the pty from an other package.

We could also have put ptyMaster public, but then we need to ignore it in json
otherwise the Marshalling fails. I think it is cleaner that way.
Make the PTY in raw mode before assert test (TestAttachDetach)
Actually test the detach (was not the case before)
Fix term.RestoreTerminal behavior
Make sure the termcaps are restored after hijack
Create helper function for tests
Fix TestAttachDetachTruncatedID (behavior + tty issue)
Remove an unit test from integrations test
Fix behavior of tty tests
Reduce the timeout for restart/stop
Merge branch 'master' into fix_tests
Add unit test to check bind / server side
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 pull request #2954 from creack/fix_tests

Fix tests