Fix NPE in DefaultRequestDirector

When the HTTP client encountered a server failure while
talking through a proxy, it fails with an NullPointerException
and not an IOException.

Bug: http://b/5372438
Change-Id: I67848d52f5d01c9e353fcc7d66d48ec821d9b4ba
diff --git a/src/org/apache/http/impl/client/DefaultRequestDirector.java b/src/org/apache/http/impl/client/DefaultRequestDirector.java
index bfdddd6..9f6d832 100644
--- a/src/org/apache/http/impl/client/DefaultRequestDirector.java
+++ b/src/org/apache/http/impl/client/DefaultRequestDirector.java
@@ -452,7 +452,7 @@
                             managedConn.open(route, context, params);
                         } else {
                             // otherwise give up
-                            retrying = false;
+                            throw ex;
                         }
                         
                     }