Revert patches

It is important to have traceable code. This means that any person inspecting the bug tracker, Gerrit changes or the commit log shall be able to trace if a patch has been reverted. Therefore we must add this information to all affected places.

If there's the need to revert a patch, please stick to the following rules:

1. Create a ticket on Forge for the revert, if there's not yet a bug report. (Maybe re-use the original ticket, if you re-push the patch again with the original ticket number.)

2. Visit the original ticket in Forge and

   1. link it to the revert ticket
   2. add a comment to the ticket with information that it is reverted
   3. set the Status from Resolved to Accepted
3. Use the Revert button in Gerrit

4. Modify the commit message of the newly created patch to contain

   1. the commit hash as generated by Gerrit
   2. a description why the revert is needed
   3. a Releases-line that contains all releases where the original patch was merged (check if the backports where really merged)
   4. a Resolves-line for the revert ticket as created above (you can skip this if you re-used the original ticket)
   5. a Reverts-line for the ticket of the original patch