QA » openQA Project

## Observation

https://build.opensuse.org/package/live_build_log/devel:openQA:TestGithub:OPR-1924/os-autoinst/openSUSE_15.3/x86_64 showed

```
[ 206s] 3: # Failed test 'log output for backend driver creation'
[ 206s] 3: # at ./29-backend-driver.t line 24.
[ 206s] 3: # STDOUT & STDERR:
[ 206s] 3: # hannel_in 20
[ 206s] 3: # [0m
[ 206s] 3: # don't match:
[ 206s] 3: # (?^u:(Blocking SIGCHLD|channel_out))
[ 206s] 3: # as expected
[ 206s] 3: # Looks like you failed 1 test of 12.
[ 206s] 3: [13:25:34] ./29-backend-driver.t ....................
[ 206s] 3: not ok 1 - log output for backend driver creation
```

I have seen this at least twice but AFAIR only in OBS checks

## Acceptance criteria
* **AC1:** 29-backend-driver.t doesn't fail is stable in OBS checks

## Suggestions
* Just add t/29-backend-driver.t to the exclude list in dist/rpm/os-autoinst.spec