Bug#784688: Thousands of "xen:balloon: Cannot add additional memory (-17) messages" despite dom0 ballooning disabled

[KSB <ksb@inbox.lv>]

> Do you have a package version which you know to be good? How confident are
> you that it is ok (sometimes the problem is intermittent)?
>
> Lastly, is there any chance you upgraded the Xen packages at the same time?
> I'm starting to wonder if maybe this is not a kernel issue.
Sorry, but there is chance, sadly.

But I checked logs more thoroughly and found it even on more recent kernels:
1) Lot of messages on 3.14-2-amd64 with xen-4.6, 13 domU's.
2) 4.3.0-1-amd64 xen-4.6, only two messages shortly after boot, only 1 
domU running:
[   12.473778] xen:balloon: Cannot add additional memory (-17)
[   21.673298] xen:balloon: Cannot add additional memory (-17)
uptime 17 days.

Previous on same machine was 4.2.0-1-amd64 with more (-17)'s

3) 4.3.0-1-amd64, one month, several reboots, average 4 domU's, and no 
messages

4) 3.16.0-4-amd64, xen-4.1, 22 domU's, uptime 188 days, in last month I 
see only
Jan 7 14:12:08
Jan 7 14:12:08
Jan 7 14:12:08
Jan 7 14:12:08
Jan 7 14:27:47
Jan 7 14:27:47
Jan 7 14:27:47
Jan 7 14:27:48
and this is roughly the time last machine was created(started).