[octane] Repos for 6.1 are not deleted during upgrade 6.0 to 7.0

[Ekaterina Shutova]

While upgrading 6.0 to 7.0 i've found repositories for 6.1 are not deleted properly.

Steps to reproduce:
1) Install fuel mos6.0 and deploy simple cluster(for example, controller + compute/cinder)
2) Upgrade 6.0 to 7.0 using this instruction: https://mirantis.jira.com/wiki/display/PDT/HOW-TO%3A+Upgrade+Fuel+master+MOS6.0+to+MOS8.0
3) Go to master node and try to upload 7.0 MU updates(to have latest version of fuel-octane and other packages) according to this instruction: https://mirantis.jira.com/wiki/display/QA/How+to+Test+Maintance+Updates
4) Upgdate to 8.0

Expected result:
Updates are installed correctly and upgrade to 8.0 was performed successfully.
Actual result:
Repositories for 6.1 were not deleted after upgrade.
[root@nailgun 7.0]# ls /etc/yum.repos.d
6.1_nailgun.repo 7.0_nailgun.repo mos6.1-security.repo mos7.0-security.repo nailgun.repo
7.0_auxiliary.repo auxiliary.repo mos6.1-updates.repo mos7.0-updates.repo

If I delete 6.1-related repositories manually, then a lot of conflicts during yum update:
https://kobra.io/#/e/-KMdP4FiLezFkohlcOUm
[root@nailgun ~]# docker load -i /var/www/nailgun/docker/images/fuel-images.tar

Message from syslogd@nailgun at Jul 14 10:36:26 ...
 kernel:journal commit I/O error
FATA[0277] Error: Driver devicemapper failed to create image rootfs badc957da39094297c770f96705e38b004816c21d20b6e6cc11696a5e2380959: Error running DeviceCreate (createSnapDevice) dm_task_run failed

Impossible to install MU updates for 7.0.

Reproducibility:
tried several times on two servers - 100%.

Workaround:
Not found yet.

[Ilya Kharin (akscram)]

Due to the fact that we can't fix this problem in upgrade tarballs because it requires some extra time to rebuild them (I'm not sure that's event possible). So, at least we need to find solution how to remove them and document it.

[Anton Matveev (amatveev)]

octane specific, moving to won't fix due to shifted priorities