Reset row_sent at end of query

We need to reset row_sent to false at the end of the query so that we
will emit '{"rows":{' for the next query (if we're in a multi-query
request).

COUCHDB-3060
diff --git a/src/couch_mrview_http.erl b/src/couch_mrview_http.erl
index 341495e..529d208 100644
--- a/src/couch_mrview_http.erl
+++ b/src/couch_mrview_http.erl
@@ -382,7 +382,7 @@
             {ok, Resp2} = chttpd:end_delayed_json_response(Resp1),
             {ok, Acc#vacc{resp=Resp2}};
         _ ->
-            {ok, Acc#vacc{resp=Resp1,
+            {ok, Acc#vacc{resp=Resp1, row_sent=false,
                 prepend=",\r\n", buffer=[], bufsize=0}}
     end;
 view_cb({error, Reason}, #vacc{resp=undefined}=Acc) ->