By David Barron After almost a half-century as a pitcher, sales representative, broadcaster, manager and goodwill ambassador for Houston’s Major League Baseball franchise, Larry Dierker’s association with the Astros will end April 15. The end of the relationship, Dierker said this week, stems in large part from his disappointment and frustration that he was not allowed a chance to return to the broadcast booth this season. He said he met Wednesday with team marketing officials and refused to sign a contract that would have called on him to do up to 180 appearances on the team’s behalf each year. “I told them from the start that if it’s not meaningful [...]