Avoid compile warning in tst_qftp

setSession is only used if we have bearer management.

Change-Id: I64b9d29c01566e79bbca5d0dc11d6aee6d9b0bf0
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@qt.io>

tests/auto/network/access/qftp/tst_qftp.cpp

@@ -248,6 +248,8 @@ void tst_QFtp::init()
     } else {
         networkSessionExplicit.clear();
     }
+#else
+    Q_UNUSED(setSession);
 #endif
 
     delete ftp;