Fix error/debug messages in Container.Attach and recover from ErrClosedPipe conditions.
Merge pull request #2242 from jpetazzo/remove-spurious-errors-and-errclosedpipe

Fix error/debug messages in Container.Attach and recover from ErrClosedPipe
Merge branch 'master' into bump_0.6.4

Clean up error reporting for io.ClosedPipe