accounting: allow Associate role to pass transitions on accounting transactions
f0808ac6 (workflow: add workflow transition guard for non-user actions as well., 2015-11-18) broke some custom security configurations where doing an action on a document would modify an accounting transaction - but the user doing this action does not have access to accounting.
This repairs the situation for accounting, by using the Associate role. The idea is that for such patterns where users "do something which will interact with accounting", the users also need an Associate role on accounting transaction portal types, which is in line with the meaning of Associate.