The FBI agent brother of an NYPD cop accused in a murder-for-hire plot killed himself while out of town with other agents, law-enforcement sources told The Post on Wednesday. Salvatore “Sal” Cincinelli, 41, was found with at least one gunshot wound inside the Container Bar in Austin, Texas, when cops arrived there shortly before midnight on July 16 in response to a report of gunfire, a spokeswoman for the Austin Police Department said. The incident is being investigated as suicide, the spokeswoman said. She wouldn’t elaborate. Cincinelli was a former Wall Street trader who joined the FBI in 2011 and...