Resolve "Bug - Download scenario file in list of scenarios don't works"

Closes #593 (closed)

After this fix

It works in Asqatasun 5-SNAPSHOT : download scenario file in list of scenarios is works

Before this fix

It is no longer possible to "Download" scenario file in list of scenarios.

• It works in Asqatasun 4, but not in Asqatasun 5.0.0-rc1 and 5-SNAPSHOT
• Firefox indicates that it cannot read the file.
• See log:

java.lang.IllegalStateException: getOutputStream() has already been called for this response
 	at org.apache.catalina.connector.Response.getWriter(Response.java:584)
 	at org.apache.catalina.connector.ResponseFacade.getWriter(ResponseFacade.java:227)
 	at javax.servlet.ServletResponseWrapper.getWriter(ServletResponseWrapper.java:114)
        ....
ERROR org.apache.catalina.core.ContainerBase.[Tomcat].[localhost].[/].[jsp] - Servlet.service() for servlet [jsp] threw exception
 java.lang.IllegalStateException: getOutputStream() has already been called for this response
 	at org.apache.catalina.connector.Response.getWriter(Response.java:584)
 	at org.apache.catalina.connector.ResponseFacade.getWriter(ResponseFacade.java:227)
 	at javax.servlet.ServletResponseWrapper.getWriter(ServletResponseWrapper.java:114)
        ...
ERROR org.apache.catalina.core.ContainerBase.[Tomcat].[localhost].[/].[dispatcherServlet] - Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is java.lang.IllegalStateException: getOutputStream() has already been called for this response] with root cause
 java.lang.IllegalStateException: getOutputStream() has already been called for this response
 	at org.apache.catalina.connector.Response.getWriter(Response.java:584)
 	at org.apache.catalina.connector.ResponseFacade.getWriter(ResponseFacade.java:227)
 	at javax.servlet.ServletResponseWrapper.getWriter(ServletResponseWrapper.java:114)
        ...
ERROR org.apache.catalina.core.ContainerBase.[Tomcat].[localhost].[/].[dispatcherServlet] - Servlet.service() for servlet [dispatcherServlet] threw exception
 javax.servlet.ServletException: Could not resolve view with name 'error' in servlet with name 'dispatcherServlet'
 	at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1353)
 	at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1118)
 	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1057)
        ...
ERROR org.apache.catalina.core.ContainerBase.[Tomcat].[localhost] - Exception Processing ErrorPage[errorCode=0, location=/error]
 javax.servlet.ServletException: Could not resolve view with name 'error' in servlet with name 'dispatcherServlet'
 	at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1353)
 	at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1118)
 	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1057)
 	...