Azure EventHubs binding: Remove "close by interrupt signal" logic

[pkedy]

Expected Behavior

This component has a client to cleanup. The Dapr runtime now calls Close() error on any component that implements io.Closer. Logic to cleanup should be moved there.

Actual Behavior

Currently it uses a signal channel to wait to close itself.

RELEASE NOTE: FIX Azure EventHubs binding implements Close() for cleanup

[CodeMonkeyLeet]

/assign

[CodeMonkeyLeet]

Closing this issue as the addition and the move of logic into Close() error is handled by #1093.

Using dapr/dapr#3555 to track the broader question of replacing wait on SIGTERM with appropriate cancellation contexts.