Persistent directory for container in execdriver

This is needed for persistent namespaces

Signed-off-by: Alexandr Morozov <lk4d4math@gmail.com>
Test on execdriver dir behavior

Signed-off-by: Alexandr Morozov <lk4d4math@gmail.com>
Make sure COPY/ADD on dirs doesn't grab too many files
Add check for / first - per LK4D4's comment.
Add a comment to explain why we're adding a /

Signed-off-by: Doug Davis <dug@us.ibm.com>
Merge pull request #8186 from duglin/ErrInCopyCache

Make sure COPY/ADD on dirs doesn't grab too many files
integration: lower timeout for stop/restart tests

Docker-DCO-1.1-Signed-off-by: Cristian Staretu <cristian.staretu@gmail.com> (github: unclejack)
Merge pull request #8192 from unclejack/lower_timeout_integ

integration: lower timeout for stop/restart tests
Merge pull request #7973 from LK4D4/persist_execdriver_dir

Persist execdriver dir