Update libcontainer dependency to 77ffd49dfedbc78a

Fixes #6256
Fixes #6383
Fixes #6414

Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@docker.com> (github: crosbymichael)
Merge pull request #6485 from crosbymichael/update-libcontainer

Update libcontainer dependency to 77ffd49dfedbc78a