BUG-1188: Missing callback to provider

When SouthboundHandler::processRowUpdate() gets invoked for a port,
the code was missing a callback to handleInterfaceUpdate() which
should be needed for all the interfaces for the given port.

Change-Id: I9016e3f7427a08a1d95669dd81b9257b66e81195
Signed-off-by: Flavio Fernandes <ffernand@redhat.com>