remove tracking of start/stop state

The underlying Bloomberg Open API already keeps track of this state and
errors appropriately.
cleanup event listeners

When there are no more outstanding requests with a correlation id in
flight, remove listeners for the event name.  This change also
introduces some logging for when listeners are added and removed.
remove cached open service promises

This change simplifies the mechanism of always opening a service without
caching the the result.  In the event of an underlying connection
failure, future requests will error appropriately.
whitespace cleanup and remove unnecessary logging