Don't keepalive connections on external upload.

Workaround for an Android OS bug.

Fixes #1

// FREEBIE

java/src/main/java/org/whispersystems/textsecure/internal/push/PushServiceSocket.java

@@ -400,6 +400,7 @@ public class PushServiceSocket {
 
     connection.setRequestMethod(method);
     connection.setRequestProperty("Content-Type", "application/octet-stream");
+    connection.setRequestProperty("Connection", "close");
     connection.connect();
 
     try {