Use openLDAP ppolicy in addition to MS AD specific attributes to determine if user is locked
Description
Right now, Gitlab can only detect deactivated users by checking a Microsoft AD specific attribute (lib/gitlab/auth/ldap/person.rb#8). Users of openLDAP (with the ppolicy overlay module) are left without this detection.
Proposal
Check for the presence of the pwdAccountLockedTime attribute on the user to determine if the user is blocked. If temporary blocks (e.g. due to password mistype) should not be respected for this decision, the value should be checked against the constant 000001010000Z for equality.