A former aide to Hillary Rodham Clinton who helped set up the server that housed Mrs. Clinton’s private email account plans to invoke his Fifth Amendment rights in response to congressional questions about the email practices, according to two people briefed on the matter. The former aide, Bryan Pagliano, was subpoenaed to testify before the House committee investigating the 2012 attacks in Benghazi, Libya. But a lawyer for Mr. Pagliano, Mark MacDougall, has told the committee that Mr. Pagliano will decline to answer their questions and assert his Fifth Amendment privilege. ​Mr. ​Pagliano was the information technology director for Mrs....