[jenkins only] introduce names for user backends - IUserBackend

[MorrisJobke]

Jenkins PR for #12819

[MorrisJobke]

@owncloud-bot retest this please

[ghost]

Refer to this link for build results (access rights to CI server needed):
https://ci.owncloud.org//job/pull-request-analyser-ng-simple/5106/

Build result: FAILURE

[...truncated 16 lines...]Fetching upstream changes from https://github.com/owncloud/core.gitusing GIT_SSH to set credentials using .gitcredentials to set credentials > git config --local credential.helper store --file=/tmp/git4859213143207446491.credentials # timeout=10 > git fetch --tags --progress https://github.com/owncloud/core.git +refs/pull/:refs/remotes/origin/pr/ > git config --local --remove-section credential # timeout=10 > git rev-parse origin/pr/12953/merge^{commit} # timeout=10 > git branch -a --contains e85c85ad09deb7d5cace939d0b2fa81cf14534a5 # timeout=10 > git rev-parse remotes/origin/pr/12953/merge^{commit} # timeout=10Checking out Revision e85c85ad09deb7d5cace939d0b2fa81cf14534a5 (origin/pr/12953/merge) > git config core.sparsecheckout # timeout=10 > git checkout -f e85c85ad09deb7d5cace939d0b2fa81cf14534a5First time build. Skipping changelog. > git remote # timeout=10 > git submodule init # timeout=10 > git submodule sync # timeout=10 > git config --get remote.origin.url # timeout=10 > git submodule update --init --recursiveTriggering pull-request-analyser-ng-simple » SLAVEpull-request-analyser-ng-simple » SLAVE completed with result FAILUREStarted calculate disk usage of buildFinished Calculation of disk usage of build in 0 secondsStarted calculate disk usage of workspaceFinished Calculation of disk usage of workspace in 1 second
Test FAILed.