feat(worker): add support for conditional connection closure

[kibertoad]

fixes #2437

In case application manages lifecycle of Redis connection itself, this provides an option of opting out of BullMQ automatic connection close.

[manast]

This is not needed. The underlying Redis connection is only closed if it is not "shared": https://github.com/taskforcesh/bullmq/blob/master/src/classes/redis-connection.ts#L297