Fix unattended-upgrades after deb repo modification

unattended-upgrades doesn't work properly anymore for the leap deb repo.

root@donkey:~# unattended-upgrade --dry-run --debug
Initial blacklisted packages: 
Initial whitelisted packages: 
Starting unattended upgrades script
Allowed origins are: ['origin=Debian,codename=jessie,label=Debian', 'origin=Debian,codename=jessie,label=Debian-Security', 'site=deb.leap.se,component=master', 'site=deb.leap.se,component=master']
adjusting candidate version: '<Version: package:'python-leap-common' version:'0.6.2+0~20171003164702.21584+master+jessie~1.gd7d3c83'>'
adjusting candidate version: '<Version: package:'soledad-client' version:'0.10.3+0~20171017171540.23264+master+jessie~92.gb3bf0be'>'
adjusting candidate version: '<Version: package:'soledad-common' version:'0.10.3+0~20171017171540.23264+master+jessie~92.gb3bf0be'>'
pkgs that look like they should be upgraded: 
Fetched 0 B in 0s (0 B/s)                                                                                                                                                                                         
fetch.run() result: 0
blacklist: []
whitelist: []
InstCount=0 DelCount=0 BrokenCount=0
No packages found that can be upgraded unattended


root@donkey:/etc/apt/apt.conf.d# apt-cache policy | grep -i leap -A3
 999 http://deb.leap.se/platform/ master/jessie amd64 Packages
     release n=master,c=jessie
     origin deb.leap.se
 500 http://deb.debian.org/debian/ jessie-backports/main Translation-en
 100 http://deb.debian.org/debian/ jessie-backports/main amd64 Packages
     release o=Debian Backports,a=jessie-backports,n=jessie-backports,l=Debian Backports,c=main

root@donkey:/etc/apt/apt.conf.d# cat /etc/apt/apt.conf.d/51unattended-upgrades-leap
// this file is managed by puppet !

Unattended-Upgrade::Origins-Pattern {
  "site=deb.leap.se,component=master";
}

Changing 51unattended-upgrades-leap to use

"site=deb.leap.se,n=master";

would fix the problem.

But I don't know what n= is the abbreviation for :o