This change fix license boilerplate and its copyright.
The updated year in copyright is based on the file creation date.
If older than 2021, added copyright is transfered to multus
authors from Intel corporation as the multus code was officially
transfered to Kubernetes Networking Plumbing Working Group on
March 11, 2021.
This changes introduce delegate API function in multus-daemon.
This API will be consumed from other programs for hot-plug
interface into running pod. This change also cleanups server
code to split into client code and server code to easy to import
from other golang code.
