NFD

Presently, NFD creates the Unix socket at /run/nfd.sock.
This causes difficulty in NFD Docker packaging: either the container must mount /run in read-write mode which gives the container too much privilege, or the client.conf must be edited to point to a different socket path.

This issue is to change the default Unix socket path path to /run/nfd/nfd.sock, without any backwards compatibility.
NFD must create the enclosing directory if it does not exist.