Fix create memif socket

Fix create memif socket

create interface memif [id <id>] [socket-id <socket-id>] ...

Can optionally take a socket-id.

You create a socket-id with:

create memif socket [id <id>] [filename <path>]

Unfortunately, this doesn't work because "create memif" was
deprecated.  It results in:

vpp# create memif socket id 0 filename /run/vpp/test.socket
command deprecated. Please use 'create interface memif' instead.

This fixes it by clipping out the

create memif

command entirely.

Change-Id: If503758706bf758b6cb46e958200527a5856c600
Signed-off-by: Ed Warnicke <hagbard@gmail.com>