close-connection causes websocket read thread to spin and use 100% CPU

[eeeeeta]

When calling wsd:close-connection on a connection object, the websocket read thread associated with that object starts using 100% CPU trying to call READ-SEQUENCE, erroring out (because the stream is closed), and then for some reason it ignores the error and retries ad infinitum.

I worked around this with bt:destroy-thread in my application, but ideally the read thread should be properly closed when the connection is... (and, for that matter, probably shouldn't ignore read errors either)