Feature/msp 9950/migrate old creds

### Verification

- [ ] `rails c`
- [ ] `cred = FactoryGirl.build(:mdm_cred)`
- [ ] Verify value exists: `cred.pass`
- [ ] Verify value exists: `cred.ptype`
- [ ] Verify value exists: `cred.user`
- [ ] Verify value exists: `cred.active`