Update global-jjb to latest master

Pulls in a quick fix to set the default python back to py2
for tox-verify jobs.

Change-Id: I6d1a5c8dec30166ac5d6045543174c380054cd61
Signed-off-by: Thanh Ha <thanh.ha@linuxfoundation.org>

diff --git a/jjb/global-jjb b/jjb/global-jjb
index c00e75c79a275db041585fe532ab0a36169c3c38..c1873360fa7455fdb690c6235923d7eb68e30ec6 160000 (submodule)
--- a/jjb/global-jjb
+++ b/jjb/global-jjb
@@ -1 +1 @@
-Subproject commit c00e75c79a275db041585fe532ab0a36169c3c38
+Subproject commit c1873360fa7455fdb690c6235923d7eb68e30ec6