TransportAction currently contains 2 doExecute methods, one which takes
a the task, and one that does not. The latter is what some subclasses
implement, while the first one just calls the latter, dropping the given
task. This commit combines these methods, in favor of just always
assuming a task is present.
Most transport actions don't need the node ThreadPool. This commit
removes the ThreadPool as a super constructor parameter for
TransportAction. The actions that do need the thread pool then have a
member added to keep it from their own constructor.
Most transport actions don't need to resolve index names. This commit
removes the index name resolver as a super constructor parameter for
TransportAction. The actions that do need the resolver then have a
member added to keep the resolver from their own constructor.