BUG-768 Texture fetches hit caps throttle and need more retries.

Bumped the default retry limit up from 5 to 8 which gives up to
15 seconds more dwell time should the viewer get a 503 or other
recoverable error on access.

indra/llcorehttp/_httpinternal.h

@@ -111,7 +111,15 @@ const int HTTP_TRACE_MIN = HTTP_TRACE_OFF;
 const int HTTP_TRACE_MAX = HTTP_TRACE_CURL_BODIES;
 
 // Request retry limits
-const int HTTP_RETRY_COUNT_DEFAULT = 5;
+//
+// At a minimum, retries need to extend past any throttling
+// window we're expecting from central services.  In the case
+// of Linden services running through the caps routers, there's
+// a five-second or so window for throttling with some spillover.
+// We want to span a few windows to allow transport to slow
+// after onset of the throttles and then recover without a final
+// failure.  Other systems may need other constants.
+const int HTTP_RETRY_COUNT_DEFAULT = 8;
 const int HTTP_RETRY_COUNT_MIN = 0;
 const int HTTP_RETRY_COUNT_MAX = 100;