Clatd changes for move of libipchecksum.

libipchecksum is becoming its own library in
frameworks/libs/net and its include files are no longer under
netutils/. Adjust clatd code accordingly.

Also reorder some include files as suggested by clang-format.

Test: m
Test: atest clatd_test
Test: connects to IPv6-only wifi, testipv4.com shows 10/10
Change-Id: I5e4c73065ce828123aef7e8851227f9bdf444ff9
diff --git a/clatd_test.cpp b/clatd_test.cpp
index 9b7a3e7..d6d7e66 100644
--- a/clatd_test.cpp
+++ b/clatd_test.cpp
@@ -30,10 +30,10 @@
 #include "tun_interface.h"
 
 extern "C" {
+#include "checksum.h"
 #include "clatd.h"
 #include "config.h"
 #include "getaddr.h"
-#include "netutils/checksum.h"
 #include "translate.h"
 }