EE Migration causes problems upgrading from CE to EE
Commit af2b5879 introduced a bug when upgrading from CE to EE. The header_logo
column already exists from migration https://gitlab.com/gitlab-org/gitlab-ee/blob/master/db/migrate/20160222153918_create_appearances_ce.rb. We need to guard this column rename to avoid causing problems.
cc/ @zj Can you take a look, please?