LP1912834 OpenSRF JS Max Parallel Requests

LP1912834 OpenSRF JS Max Parallel Requests

Limit the number of active network requests coming from OpenSRF
(WebSocket, XHR) to avoid flooding servers with excessive numbers of
active requests.

The value is currently hardcoded to 5 in opensrf.js.

When the max number of requests limit is reached and new requests
continue to arrive, a warning message is logged to notify the developer
to consider refactoring the client code to use batched calls / API's.

Signed-off-by: Bill Erickson <berickxx@gmail.com>