unused import
Connectors can be a single client in a threadlocal now.

We only needed the map to account for clients configured with multiple differing configs.  This in turn only occurred during topology submission, where we connected to each table in turn to get its metadata.

That's now done in the scheduler (which avoids this code path.)  Further, at runtime we know that a given executor thread will only ever run tasks sharing a common component.  Therefore only one config will ever be in scope for a given executor thread, and we can drop the map.
Use ExecutorScoped to inject thread-local connector.
Inject the ScheduledExecutorService directly.

This relieves HTableConnector from provisioning it directly.
No need for this test setter here.
Inject ScheduledExecutorService in HBaseComponent.