Update to global-jjb v0.21.0

Change-Id: I64f6e49ccc983ecc292cc42c1868e494af5cd0de
Signed-off-by: Anil Belur <abelur@linuxfoundation.org>

diff --git a/jjb/global-jjb b/jjb/global-jjb
index 5a2ef9c64caf06ff737dfa040b61c4909c97e996..2b4fca8ba1a2f7862ebd771d0111c7cbd4e442bf 160000 (submodule)
--- a/jjb/global-jjb
+++ b/jjb/global-jjb
@@ -1 +1 @@
-Subproject commit 5a2ef9c64caf06ff737dfa040b61c4909c97e996
+Subproject commit 2b4fca8ba1a2f7862ebd771d0111c7cbd4e442bf