(Reuters) - Websense Inc said it had agreed to be taken private by Vista Equity Partners in a deal that values the online security firm at about $907 million, a move that should come as a relief to investors after years of weak sales from its legacy business. The offer of $24.75 per share represents a roughly 29 percent premium to Websense's Friday close. Websense shares rose to just above the offer price to a near two-year high in morning trading on the Nasdaq. ...