Provide a valid default port when parsing QUrl

When port is not specified in QUrl, the default value is
returned. This default value is -1, which was promptly cast to an
unsigned integer.

src/qamqp/amqp.cpp

@@ -111,7 +111,7 @@ void ClientPrivate::parseCnnString( const QUrl & con )
 		q->setSsl(con.scheme() == AMQPSSCHEME);
 		q->setPassword(con.password());
 		q->setUser(con.userName());
-		q->setPort(con.port());
+		q->setPort(con.port(AMQPPORT));
 		q->setHost(con.host());				
 		q->setVirtualHost(con.path());
 	}