[Bugfix beta] Route#render name vs viewName precedence fix

Fixes #4248: Passing an explicit name parameter to Route#render
should not have the associated view for that name be overriden
by Route#viewName.
This ensures that in the case of rendering to multiple outlets, and
later changing the viewName property, the only outlet to have its
view changed should be the main one.
Merge pull request #4249 from oskarols/render-viewname-fix

[BUGFIX #4248] Route#viewName overriding explicit name parameter when calling render method