Just because CEO John Chambers is selling Cisco (Nasdaq: CSCO) stock, should you? It’s a question posed on investment site Seeking Alpha regarding Chambers’ plan to sell about a third of his position. The answer? Maybe. If investors are concerned about rising tax rates and want to lock in gains at a lower rate, it might be time to sell your position and get back into the game at a lower price, the author postulates. While anytime a CEO sells his company stock alarm bells can sound, Chambers…