Method poll

src/main/java/org/sfj/LittleCASPaxos.java:274–274

Poll for a value. (use under lock for this key) @param key key @return null if not existent, or the kv value in storage

(String key)

     * @return null if not existent, or the kv value in storage
     */
    KV poll(String key);

    /**
     * Get the value. (use under lock for this key)