Cleanup some statements from exec driver work
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Change now-misnamed TarFilter to TarWithOptions

Docker-DCO-1.1-Signed-off-by: Travis Cline <travis.cline@gmail.com> (github: tmc)
Add .dockerignore support

Fixes #2224

Docker-DCO-1.1-Signed-off-by: Travis Cline <travis.cline@gmail.com> (github: tmc)