rgw: update civetweb submodule

Signed-off-by: Yehuda Sadeh <yehuda@redhat.com>

diff --git a/src/civetweb b/src/civetweb
index 79d0efdabb6a707c2f7c0e65525f39c7736341ec..c39d732637a813ab5d4386a6167444dd6a235e82 160000 (submodule)
--- a/src/civetweb
+++ b/src/civetweb
@@ -1 +1 @@
-Subproject commit 79d0efdabb6a707c2f7c0e65525f39c7736341ec
+Subproject commit c39d732637a813ab5d4386a6167444dd6a235e82