JSON views from namespaced controller are not resolved when running from WAR file

This probably related with the closed issue apache/grails-views#186

**Environment**
Linux amd64, OpenJDK 1.8.0_192, Grails 3.3.9, Grails View 1.2.9

**Steps to reproduce**
1. Clone the sample project at https://github.com/delfianto/grails-json-view-test
2. Run the grails app with `run-app`
3. Test the endpoint `/message?text=hello` and `/v1/message?text=hello` (they work)
4. Build war file using `grails assemble`
5. Run the war file using `java -jar grails-json-view-test-0.1.war`
6. The endpoint with namespace will throw an exception while the endpoint without namespace works

**Description**
When the grails app is started by `run-app` command, JSON view for namespaced controllers works fine. If the application is started from a war archive somehow the view does not resolve properly, resulting in the exception below:

```
2018-12-29 14:25:45.670 DEBUG --- [0.0-9090-exec-2] g.views.ResolvableGroovyTemplateEngine : No template found for path [v1/message/index.gson] and locale [en_US]
2018-12-29 14:25:45.670 DEBUG --- [0.0-9090-exec-2] g.views.ResolvableGroovyTemplateEngine : No template found for path [v1/v1/message/index.gson] and locale [en_US]
2018-12-29 14:25:45.670 DEBUG --- [0.0-9090-exec-2] g.views.ResolvableGroovyTemplateEngine : No template found for path [index.gson] and locale [en_US]
2018-12-29 14:25:45.671 ERROR --- [0.0-9090-exec-2] .a.c.c.C.[.[.[.[grailsDispatcherServlet] : Servlet.service() for servlet [grailsDispatcherServlet] in context with path [] threw exception [Could not resolve view with name 'index' in servlet with name 'grailsDispatcherServlet'] with root cause

javax.servlet.ServletException: Could not resolve view with name 'index' in servlet with name 'grailsDispatcherServlet'
at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1266)
at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1041)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:984)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:901)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970)
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:861)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:635)
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:742)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.springframework.boot.web.filter.ApplicationContextHeaderFilter.doFilterInternal(ApplicationContextHeaderFilter.java:55)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.springframework.boot.actuate.trace.WebRequestTraceFilter.doFilterInternal(WebRequestTraceFilter.java:111)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.grails.web.servlet.mvc.GrailsWebRequestFilter.doFilterInternal(GrailsWebRequestFilter.java:77)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.grails.web.filters.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:67)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:197)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.springframework.web.filter.CorsFilter.doFilterInternal(CorsFilter.java:96)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.springframework.boot.actuate.autoconfigure.MetricsFilter.doFilterInternal(MetricsFilter.java:103)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:493)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:800)
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:806)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1498)
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:748)
```

Start with the linked sample project and reproduce the difference between `run-app` and `java -jar` after `grails assemble`. Compare `/message` with `/v1/message` and trace the reported `ResolvableGroovyTemplateEngine` lookup paths. Done means the namespaced endpoint resolves its JSON view successfully from the WAR without breaking the unnamespaced endpoint.

Written by the indexing model from the issue text.