The server now cancels an observe relation if a request has the observe
option set with any nonzero value (Before it would have only canceled it
if the value was 1). This behavior is requested by observe-14 chapter
4.1.
Fixed a bug where a CoapObserveRelation object did not remember over
which (client) Endpoint the relation had been established with the
server and had later used the default endpoint in attempt to proactively
cancel the relation. Now, the CoapObserveRealtion object correctly uses
the same (client) Endpoint to establish and cancel observe relations.
Extended a test and fixed a bug where the server-side matcher did not
remove entries (for NON notifications) from the HashMap exchangesByMID
after an observe relation had been proactively canceled.