[REF] Determine values where they are needed rather than passing them around

[REF] Determine values where they are needed rather than passing them around

The membershipTypes array is constructed, but barely used. One place it is used
is in this function - which is explictly tested by CRM_Member_Form_MembershipTest::testSubmit

This fixes it to get the values when needed rather than construct a variable miles away from
where it is used - no more pass the parcel