Imports of vpnkit-list-ports command

PathSynopsis
contextPackage context defines the Context type, which carries deadlines, cancellation signals, and other request-scoped values across API boundaries and between processes.
flagPackage flag implements command-line flag parsing.
fmtPackage fmt implements formatted I/O with functions analogous to C's printf and scanf.
github.com/moby/vpnkit/go/pkg/vpnkitPackage vpnkit allows a running VPNKit service to be reconfigured.
logPackage log implements a simple logging package.
osPackage os provides a platform-independent interface to operating system functionality.