distro: introduce upstream cznic release prefix

using cznic.1 release string for upstream packages ensures they are prefered over downstream ones and that their versions don't collide which was causing issues for users with both downstream and upstream packaging repos enabled.

Following statements are true according to dpkg --compare-versions:

1.2.3-1   < 1.2.3-cznic.1
1.2.3-999 < 1.2.3-cznic.1

So upstream packages should always take precedence over downstream packages of the same version.