[chronik-client] Make sure we have a listener attached when emitting the ready status event

Summary:
Otherwise wait for a bit and retry in a loop. Mocha will eventually time out if no listener is ever attached. Also do the same for ecash-lib.

This will fix most of the integration test failures.

Test Plan:

npm run integration-tests

Reviewers: #bitcoin_abc, bytesofman

Reviewed By: #bitcoin_abc, bytesofman

Differential Revision: https://reviews.bitcoinabc.org/D16095