Refactor IT code for re-use...

Refactor IT code for re-use...

..and to solve race condition in NetvirtIT

1. NotifyingDataChangeListener moved into mdsal-utils
2. NodeInfo moved into new it-utils. The original
thought was to place this in southbound-utils but it
has some dependencies on net-virt code. Instead,
create it-utils which since it is designated for IT
can really depend on everything.
3. Created ItUtils class. Eventually this could and
should hold more generic IT functions, e.g.,
validateFlow, etc. There is more to do here but wanted
to get this code review rolling. This can be just phase
one.

Change-Id: I23645bfbe54762516b182446a93577ee0033e828
Signed-off-by: Josh <jhershbe@redhat.com>