oslo_log should be used instead of oslo-incubator. This fixes an error "oslo_config.cfg.DuplicateOptError: duplicate option: default_log_levels" when os-brick is imported to projects using oslo_config and oslo_log. Change-Id: Ic38c548bd39bc8ce68bd70d2b0693f6d0c0c5399 Closes-Bug: #1443681