ci.mariadb.org save release branches packages separately

Currently, builds are stored together at ci.mariadb.org. When the disk becomes full, older builds are automatically deleted. This causes problems when a release is coming soon. It is possible that the release binaries end up getting deleted, before they are uploaded to the mirrors. To fix this problem, we should specialize saving particular branches separately and not delete the most recent n (let n be 5) builds for those branches.

Those branches are:

• bb-10.x-release
• 10.x