[DLM] zero unused parts of sockaddr_storage

When we build a sockaddr_storage for an IP address, clear the unused parts as
they could be used for node comparisons.

I have seen this occasionally make sctp connections fail.

Signed-Off-By: Patrick Caulfield <pcaulfie@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>