sockets_offload_poll_wrapper: cancel work before socket close

[mniestroj]

So far there was a possibility that work item was in both RUNNING and QUEUED states. As a result of zsock_close() call, threaded (executed from workqueue) zsock_poll() returned. However just because work was QUEUED, sock_wrapper_poll_handler() was entered once again by workqueue thread. Subsequent work cancellation with k_work_cancel_sync() could no longer be finished, as work was waiting once again on zsock_close().

Start work cancellation using k_work_cancel() just before zsock_close() is invoked. This clears QUEUED state from work item, so sock_wrapper_poll_handler() is not reentered. After zsock_close() has returned, it is safe to call k_work_cancel_sync() to finish work cancellation and make sure that sock_wrapper_poll_handler() (hence zsock_poll()) is no longer running.

[github-actions[bot]]

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