[1.5.x] Fixed #19519 -- Fired request_finished in the WSGI iterable's close().

Backport of acc5396.

tests/regressiontests/handlers/urls.py

@@ -0,0 +1,9 @@
+from __future__ import unicode_literals
+
+from django.conf.urls import patterns, url
+from django.http import HttpResponse, StreamingHttpResponse
+
+urlpatterns = patterns('',
+    url(r'^regular/$', lambda request: HttpResponse(b"regular content")),
+    url(r'^streaming/$', lambda request: StreamingHttpResponse([b"streaming", b" ", b"content"])),
+)