[dist/ci,webui] Update Jenkins job templates to recent discoveries.

[dist/ci,webui] Update Jenkins job templates to recent discoveries.

Don't recommend discarding results anymore. Let all jobs archive their
artificats (Jenkins-speech for "allow other jobs to copy from job's
workingdir"). No need to change $bsdir in BSConfig.pm, testsuites do
that anyway. Fix more executable bits in obs_testsuite_api. The coverage
reports are found under src/{api,webui}/coverage/test. Remove logfiles
after test run, they only waste space.

Also let the webui require the 'ci_reporter' gem to generate test
reports.