civetweb: pullup chunked encoding by Marcus

Fixes: http://tracker.ceph.com/issues/19736
Signed-off-by: Matt Benjamin <mbenjamin@redhat.com>

diff --git a/src/civetweb b/src/civetweb
index 47e4be125f194598ab8a25599767468220b9f4ae..9fb67a7dfd4b497d6381c0d051cddd2ce632d476 160000 (submodule)
--- a/src/civetweb
+++ b/src/civetweb
@@ -1 +1 @@
-Subproject commit 47e4be125f194598ab8a25599767468220b9f4ae
+Subproject commit 9fb67a7dfd4b497d6381c0d051cddd2ce632d476