[bug]: wt disk overflow queue test flake

[ellemouton]

Ran into this during a CI run. This code has been in for a long time and I havent seen this before so probably some
edge case that needs some careful investigation.

--- FAIL: TestDiskOverflowQueue (1.68s)
    --- FAIL: TestDiskOverflowQueue/start_stop_queue (2.67s)
        queue_test.go:298: task 40250 not received in time
    --- FAIL: TestDiskOverflowQueue/startup_with_smaller_buffer_size (2.81s)
        queue_test.go:318: 
            	Error Trace:	/home/runner/work/lnd/lnd/watchtower/wtclient/queue_test.go:318
            	            				/home/runner/work/lnd/lnd/watchtower/wtclient/queue_test.go:183
            	            				/home/runner/work/lnd/lnd/watchtower/wtclient/queue_test.go:69
            	Error:      	Received unexpected error:
            	            	predicate not satisfied after time out
            	Test:       	TestDiskOverflowQueue/startup_with_smaller_buffer_size
    queue_test.go:406: [ERR]: Could not load next task from disk. Retrying.