Cancel outbound operations only in the osd_client_t destructor

This is required to prevent disconnected peers from sometimes receiving messages
suited for other peers - stop_client was freeing the operations even though they
were still references in the io_uring requests in progress. This was leading to
OSDs sometimes receiving garbage and "broken sequencing" errors in logs as the
memory was usually already reallocated for other operations

src/client/msgr_op.h

@@ -173,6 +173,7 @@ struct osd_op_t
     osd_op_buf_list_t iov;
 
     ~osd_op_t();
+    void cancel();
 
     bool is_recovery_related();
 };