Handle subdomain case in single version middleware

Author: ericholscher

readthedocs/core/middleware.py

@@ -150,7 +150,7 @@ def process_request(self, request):
                 # Let 404 be handled further up stack.
                 return None
 
-            if getattr(proj, 'single_version', False):
+            if getattr(proj, 'single_version', False) and not getattr(settings, 'USE_SUBDOMAIN', False):
                 request.urlconf = 'readthedocs.core.single_version_urls'
                 # Logging
                 host = request.get_host()