Do not log to /var/log/katello by default

Log by default to ./log not to /var/log/katello. Otherwise it
tries to write to /var/log/katello on developer's machine. It
is handled by a symlink (part of RPM)

    `/usr/share/katello/log -> /var/log/katello`

in deployment.
Merge pull request #2350 from pitr-ch/quick/var-log

Do not log to /var/log/katello by default