HOUSTON (Reuters) - Sometimes going undercover in Texas means no cover at all. Houston police, long thwarted in their campaign against prostitution by an internal policy that barred officers from removing their clothes, have reaped results by shedding that unwritten rule. The change in tactics that allows vice squad officers to undress in pursuit of evidence is part of a crackdown on suspected brothels that advertise themselves as day spas, lingerie modeling studios, massage parlors and "stress relief clinics." Two investigations using the new rules have resulted in organized crime charges against six business proprietors and dozens of misdemeanor prostitution...