Migrate TestGetEvents into a unit and a CLI test

Docker-DCO-1.1-Signed-off-by: Guilherme Salgado <gsalgado@gmail.com> (github: gsalgado)
Move truncindex in separate package in pkg/

Docker-DCO-1.1-Signed-off-by: Alexandr Morozov <lk4d4math@gmail.com> (github: LK4D4)
Improve truncindex benchmarks

Docker-DCO-1.1-Signed-off-by: Alexandr Morozov <lk4d4math@gmail.com> (github: LK4D4)
Benchmarks for engine/env

Docker-DCO-1.1-Signed-off-by: Alexandr Morozov <lk4d4math@gmail.com> (github: LK4D4)
Update libcontainer to 5210a236b92a8022a673108f347
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@docker.com> (github: crosbymichael)
Update libcontainer references
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@docker.com> (github: crosbymichael)
Rename libcontainer.Container to libcontainer.Config
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@docker.com> (github: crosbymichael)
Merge pull request #6216 from gsalgado/convert-integration-tests

Convert integration/api_test:TestGetEvents into a unit test and a CLI test
Merge pull request #6648 from LK4D4/truncindex_bench

Truncindex benchmarks
Merge pull request #6595 from LK4D4/env_benchmarks

Benchmarks for engine/env
Merge pull request #6650 from crosbymichael/update-libcontainer-post-refactor

Update libcontainer dep to 5210a236b92a8022a673108f347
Add mutex warning when specifying -icc or -ip-forward and -iptables=false

Docker-DCO-1.1-Signed-off-by: Erik Hollensbe <github@hollensbe.org> (github: erikh)