Ok going a bit deeper in, I enable the debug logging file in cups_browsed.conf and see that CUPS repeatedly reload some printers.
As soon I stop CUPS on the Debian Jessie server, the Debian Stretch client CUPS stop using 100% CPU.
I have one printer two times on the Jessie CUPS server, but with different default settings (color/black) and it look like cups-browsed load this printers repeatedly.
[...]
Wed Jun 7 20:03:04 2017 Print queue Vertrieb is for remote CUPS queue(s) and we get notifications from CUPS, using implicit class device URI implicitclass:Vertrieb
Wed Jun 7 20:03:04 2017 Loaded PPD file /tmp/00a82593d31eb for printer Vertrieb from server server1:631!
Wed Jun 7 20:03:04 2017 Editing PPD file /tmp/00a82593d31eb for printer Vertrieb, setting the option defaults of the previous cups-browsed session and inhibiting client-side filtering of the job, saving the resulting PPD in /tmp/00a82593d9516.
Wed Jun 7 20:03:04 2017 Non-raw queue Vertrieb with PPD file: /tmp/00a82593d9516
Wed Jun 7 20:03:07 2017 Unable to create/modify CUPS queue (Success)!
Wed Jun 7 20:03:07 2017 Creating/Updating CUPS queue for Vertrieb_Farbe
Wed Jun 7 20:03:07 2017 Queue has 0 duplicates
[...]