In a Grails multi-project, there are errors when the User/Role domain classes are in a separate plugin subproject

Our team has a new Grails 3.3.9 multi-project. This issue manifests almost exactly like grails/grails-spring-security-ui#56 but the work-around suggested there did not work. **Ultimately, copying the Domain classes from myplugin into the myweb subproject fixed the issue**. However, we want our Domain classes, including those for Spring Security (SecUser and SecRole) to reside in the shared plugin.

### Task List

- [x] Steps to reproduce provided
- [x] Stacktrace (if present) provided
- [x] Example that reproduces the problem uploaded to Github
- [x] Full description of the issue provided (see below)

### Steps to Reproduce

**NOTE:** If you clone the repo below, you can start with step 4

1. Setup a Grails multi-project as detailed in this article: http://www.databaseapplications.com.au/grails-multi-app.jsp
2. Add s2ui to the myweb subproject
`compile 'org.grails.plugins:spring-security-ui:3.1.2'`
3. Generate Controllers and crud gsps with s2ui-override command line:
1. `grails s2ui-override auth`
2. `grails s2ui-override layout`
3. `grails s2ui-override role com.example` (replace existing controller from earlier generate-all)
4. `grails s2ui-override user com.example` (replace existing controller from earlier generate-all)
4. `cd myweb; grails run-app`
5. Login to the app with user `admin` and password `strongPassword`.
6. Navigate to `/role/create` or `/user/create`

### Expected Behaviour

Create Role and Create User pages should load without error

### Actual Behaviour
```
Error 500: Internal Server Error
URI
/role/create
Class
org.codehaus.groovy.runtime.powerassert.PowerAssertionError
Message
Request processing failed; nested exception is org.grails.gsp.GroovyPagesException: Error processing GroovyPageView: [views/role/create.gsp:21] Error executing tag : assert bean | null
Caused by
assert bean | null
```
#### Full trace from grails:
```
Line | Method
->> 473 | createGroovyPageException in /Users/dgoodman/git/atomic-mole/web-admin/grails-app/views/role/create.gsp
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Caused by GrailsTagException: [views/role/create.gsp:21] Error executing tag : assert bean
|
null
->> 21 | throwRootCause in views/role/create.gsp
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Caused by PowerAssertionError: assert bean
|
null
->> 312 | doCall in grails.plugin.springsecurity.ui.SecurityUiTagLib$_closure10
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
| 446 | invokeTagLibClosure in org.grails.gsp.GroovyPage
| 364 | invokeTag . . . . . . . . . in ''
| 39 | doCall in Users_dgoodman_git_atomic_mole_web_admin_grails_app_views_role_create_gsp$_run_closure2
| 200 | executeClosure . . . . . . . in org.grails.taglib.TagBodyClosure
| 102 | captureClosureOutput in ''
| 213 | call . . . . . . . . . . . . in ''
| 48 | captureTagContent in org.grails.plugins.web.taglib.SitemeshTagLib
| 156 | doCall . . . . . . . . . . . in org.grails.plugins.web.taglib.SitemeshTagLib$_closure3
| 446 | invokeTagLibClosure in org.grails.gsp.GroovyPage
| 364 | invokeTag . . . . . . . . . in ''
| 42 | run in Users_dgoodman_git_atomic_mole_web_admin_grails_app_views_role_create_gsp
| 162 | doWriteTo . . . . . . . . . in org.grails.gsp.GroovyPageWritable
| 82 | writeTo in ''
| 76 | renderTemplate . . . . . . . in org.grails.web.servlet.view.GroovyPageView
| 71 | renderWithinGrailsWebRequest in org.grails.web.servlet.view.AbstractGrailsView
| 55 | renderMergedOutputModel . . in ''
| 304 | render in org.springframework.web.servlet.view.AbstractView
| 150 | renderInnerView . . . . . . in org.grails.web.sitemesh.GrailsLayoutView
| 128 | obtainContent in ''
| 63 | renderTemplate . . . . . . . in ''
| 71 | renderWithinGrailsWebRequest in org.grails.web.servlet.view.AbstractGrailsView
| 55 | renderMergedOutputModel . . in ''
| 304 | render in org.springframework.web.servlet.view.AbstractView
| 1286 | render . . . . . . . . . . . in org.springframework.web.servlet.DispatcherServlet
| 1041 | processDispatchResult in ''
| 984 | doDispatch . . . . . . . . . in ''
| 901 | doService in ''
| 970 | processRequest . . . . . . . in org.springframework.web.servlet.FrameworkServlet
| 861 | doGet in ''
| 846 | service . . . . . . . . . . in ''
| 55 | doFilterInternal in org.springframework.boot.web.filter.ApplicationContextHeaderFilter
| 317 | doFilter . . . . . . . . . . in org.springframework.security.web.FilterChainProxy$VirtualFilterChain
| 127 | invoke in org.springframework.security.web.access.intercept.FilterSecurityInterceptor
| 91 | doFilter . . . . . . . . . . in ''
| 331 | doFilter in org.springframework.security.web.FilterChainProxy$VirtualFilterChain
| 114 | doFilter . . . . . . . . . . in org.springframework.security.web.access.ExceptionTranslationFilter
| 64 | doFilter in grails.plugin.springsecurity.web.UpdateRequestContextHolderExceptionTranslationFilter
| 331 | doFilter . . . . . . . . . . in org.springframework.security.web.FilterChainProxy$VirtualFilterChain
| 54 | doFilter in grails.plugin.springsecurity.web.filter.GrailsAnonymousAuthenticationFilter
| 331 | doFilter . . . . . . . . . . in org.springframework.security.web.FilterChainProxy$VirtualFilterChain
| 158 | doFilter in org.springframework.security.web.authentication.rememberme.RememberMeAuthenticationFilter
| 331 | doFilter . . . . . . . . . . in org.springframework.security.web.FilterChainProxy$VirtualFilterChain
| 170 | doFilter in org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter
| 331 | doFilter . . . . . . . . . . in org.springframework.security.web.FilterChainProxy$VirtualFilterChain
| 200 | doFilter in org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter
| 331 | doFilter . . . . . . . . . . in org.springframework.security.web.FilterChainProxy$VirtualFilterChain
| 64 | doFilter in grails.plugin.springsecurity.web.authentication.logout.MutableLogoutFilter
| 331 | doFilter . . . . . . . . . . in org.springframework.security.web.FilterChainProxy$VirtualFilterChain
| 105 | doFilter in org.springframework.security.web.context.SecurityContextPersistenceFilter
| 331 | doFilter . . . . . . . . . . in org.springframework.security.web.FilterChainProxy$VirtualFilterChain
| 58 | doFilter in grails.plugin.springsecurity.web.SecurityRequestHolderFilter
| 331 | doFilter . . . . . . . . . . in org.springframework.security.web.FilterChainProxy$VirtualFilterChain
| 214 | doFilterInternal in org.springframework.security.web.FilterChainProxy
| 177 | doFilter . . . . . . . . . . in ''
| 77 | doFilterInternal in org.grails.web.servlet.mvc.GrailsWebRequestFilter
| 67 | doFilterInternal . . . . . . in org.grails.web.filters.HiddenHttpMethodFilter
| 1142 | runWorker in java.util.concurrent.ThreadPoolExecutor
| 617 | run . . . . . . . . . . . . in java.util.concurrent.ThreadPoolExecutor$Worker
^ 745 | run in java.lang.Thread
```
### Environment Information

- **Operating System**: Mac OS 10.11.3
- **GORM Version:** 6.1.11.RELEASE
- **Grails Version (if using Grails):** 3.3.9
- **Groovy Version:** 2.4.15
- **JDK Version:** 1.8.0_11

### Example Application

- https://github.com/dgoodman-idea/s2ui-domain-class-issue

Clone the linked example application, follow the reproduction steps, and start with myweb/grails-app/views/role/create.gsp and the SecurityUiTagLib failure around closure10. Investigate why SecUser and SecRole in the shared plugin produce a null bean, then verify that /role/create and /user/create load successfully without copying the domain classes into myweb.

Written by the indexing model from the issue text.