Fixed cache bypass caching of non-cacheable replies (ticket #21).

If cache was bypassed with proxy_cache_bypass, cache-controlling headers
(Cache-Control, Expires) wasn't considered and response was cached even
if it was actually non-cacheable.

Patch by John Ferlito.

src/http/ngx_http_upstream.c

diff --git a/src/http/ngx_http_upstream.c b/src/http/ngx_http_upstream.c
index 7e06b67..89d21d8 100644
--- a/src/http/ngx_http_upstream.c
+++ b/src/http/ngx_http_upstream.c
@@ -683,6 +683,8 @@
             return NGX_DECLINED;
         }
 
+        u->cacheable = 1;
+
         switch (ngx_http_test_predicates(r, u->conf->cache_bypass)) {
 
         case NGX_ERROR:
@@ -696,8 +698,6 @@
             break;
         }
 
-        u->cacheable = 1;
-
         c = r->cache;
 
         c->min_uses = u->conf->cache_min_uses;
@@ -2181,8 +2181,6 @@
                 ngx_http_upstream_finalize_request(r, u, 0);
                 return;
             }
-
-            u->cacheable = 1;
         }
 
         break;