seperate out the terminal functions from lxc to the pkg/term

  Since these functions are indepenent of lxc, and could be used by
  other drivers.

Docker-DCO-1.1-Signed-off-by: Vincent Batts <vbatts@redhat.com> (github: vbatts)
Move the terminal setup to execdriver, instead of ./pkg/term

  It is independent of any particular driver, but likely used by
  multiple execdrivers. Also, pkg/... is not to have any links to
  docker, which this terminal setup does.

Docker-DCO-1.1-Signed-off-by: Vincent Batts <vbatts@redhat.com> (github: vbatts)
correcting the package name for the terminal setup

Docker-DCO-1.1-Signed-off-by: Vincent Batts <vbatts@redhat.com> (github: vbatts)
Merge pull request #4308 from vbatts/vbatts-seperate_driver_term

seperate out the terminal functions from lxc