Activision has announced that the upcoming Call of Duty: Modern Warfare 4 beta will have more than just multiplayer content. The MW4 beta will also include access to the campaign mission, Entrenched, along with the upcoming Warzone mode, Resurgence Zodiac. Activision will show off some of this content during the Call of Duty: Next event on August 21. As announced previously, the beta begins with an early access period August 21-25 for people who preorder, before opening up to everyone…