Bug/msp 10976/always export logins

MSP-10976

**NOTE:** this PR may fail until the "Private already taken" bug is resolved


### Verification
- [x] `rails runner db/runners/generate-dataset.rb --host-count=5`
- [x] Capture the ID of this workspace
- [x] Point your Pro Gemfile to your local copy of this repo
- [x] `bundle install`
- [x] Bounce prosvc, Rails, delayed_job
- [x] Go to the workspace created by the runner and export the whole thing as a zip
- [x] Make a new workspace and re-import the zip
- [x] Capture the ID of this new workspace
- [x] Verify: logins from old workspace exist in new workspace after import

### Post-Merge Steps
- [ ] edit `lib/metasploit/credential/version.rb` and remove PRERELEASE
- [ ] verify that `rake spec` passes 100%
- [ ] Commit and push

#### Release the Gem

##### MRI
- [ ] `rvm use 1.9.3-p547@metasploit-credential`
- [ ] `rm Gemfile.lock`
- [ ] `bundle install && rake release`

##### JRuby
- [ ] `rvm use jruby-1.7.9@metasploit-credential`
- [ ] `rm Gemfile.lock`
- [ ] `bundle install && rake release`

#### Update Pro
- [ ] Pull latest Pro code on `staging/electro-release`
- [ ] Edit the Gemfile to point to the newly released metasploit credential
- [ ] `bundle install`
- [ ] commit and push directly to `staging/electro-release`