( cherry picked from commit e6f3fe5d upstream )

When using ActiveRecord::Base.connection.active? without a DB
connection, we get a "PG::ConnectionBad: could not connect to server"
error because ActiveRecord::Base.connection doesn't exist. By using
ActiveRecord::Base.connected? we ensure we don't get this error if
the connection is missing, which is the all point of the
Gitlab::CurrentSettings#connect_to_db? method!