fix: ensure that the parser used for the CONNECT tunnel handshake is wiped on connection close

the reconnection flow from the persistent plugin wasn't invoking Connection#idling, which was the only routine nil'ing the @parser

this made it so that a new tunnel wasn't being reestablished, because @parser was the parser with which the connection was formerly sending requests

this is fixed by a second ivar pointing to the parser used for the tunnel, which is then used for the assertion, bypassing usage of @parser and the corruption it creates on reconnect