Support non-overlapping application distribution nodes

A set of nodes, known to each other, should be able to
support an application being distributed between multiple
non-overlapping sets of nodes.  For example with nodes
A, B, C & D we have App1 distributed on A & B as well as
C & D.  Other applications may be distributed involving
some other combination of these nodes without interference.

This patch adds checks in dist_ac to ignore DAC protocol
messages for an application from nodes not included in that
application's distribution specification locally.

With this patch applications may be distributed across multiple
node sets within a set of nodes known to each other, allowing
an application to be active on more than one node, as long as
there is no overlap.