testing: Hardcode /testresults mount point in winnetou's fstab

Because do-tests runs the restore-defaults script, fstab would get reset
to the default version and the mount point wouldn't be available anymore
after stopping and restarting the guests (unless the guest images were
rebuilt in between).

testing/hosts/winnetou/etc/fstab

@@ -0,0 +1,3 @@
+/dev/vda1	/			ext3	defaults,relatime,barrier=1	0	1
+/hostshare /root/shared 9p trans=virtio,version=9p2000.L 0 0
+/testresults /var/www/testresults 9p trans=virtio,version=9p2000.L 0 0

testing/scripts/build-guestimages

@@ -62,8 +62,6 @@ do
 		execute "cp -rf $DIR/../images $LOOPDIR/var/www/" 0
 		execute "cp -rf $DIR/../css $LOOPDIR/var/www/" 0
 		execute "mkdir $LOOPDIR/var/www/testresults" 0
-		echo "echo /testresults ... >> $LOOPDIR/etc/fstab" >>$LOGFILE 2>&1
-		echo "/testresults /var/www/testresults 9p trans=virtio,version=9p2000.L 0 0" >> $LOOPDIR/etc/fstab
 		execute_chroot "a2enmod -q cgid" 0
 		execute_chroot "a2enmod -q rewrite" 0
 		execute_chroot "mkdir /var/www/certs" 0