memif: Fix a message initialization problem in VAT
memif: Fix a message initialization problem in VAT

The VAT calls to MEMIF_SOCKET_FILENAME_ADD_DEL erroneously
cleared the message memory after the M() macro call and
thus lost their message id.  Don't do that.

While in the neighborhood, prevent a string copy from
referencing data that doesn't belong to the filename string.

Change-Id: Ib4309608ed617ef4f193880ecf4a0b35fda65e51
Signed-off-by: Jon Loeliger <2c20cf3f4bac0d9467d3fe2c932e4d1e1bc1f44c@netgate.com>

vpp-dev/vpp,chrisy/vpp,FDio/vpp,vpp-dev/vpp,vpp-dev/vpp,FDio/vpp,chrisy/vpp,chrisy/vpp,FDio/vpp,chrisy/vpp,vpp-dev/vpp,vpp-dev/vpp,chrisy/vpp,vpp-dev/vpp,vpp-dev/vpp,chrisy/vpp,FDio/vpp,FDio/vpp,FDio/vpp,chrisy/vpp,FDio/vpp,chrisy/vpp,FDio/vpp