Update packer version 1.2.3

The minimum recommended version of packer required
for global-jjb packer jobs is 1.2.3 which supports
the `instance_name` configuration.

https://github.com/hashicorp/packer/blob/master/CHANGELOG.md

Change-Id: Ibd9874b8632f16d96b2a07a67235de00ce87ee50
Issue-ID: CIMAN-168
Signed-off-by: Anil Belur <abelur@linuxfoundation.org>
diff --git a/jjb/global-defaults.yaml b/jjb/global-defaults.yaml
index 450355f..9fff285 100644
--- a/jjb/global-defaults.yaml
+++ b/jjb/global-defaults.yaml
@@ -15,7 +15,7 @@
     lftools-version: <1.0.0
 
     # packer_version
-    packer-version: 1.1.3
+    packer-version: 1.3.1
 
     # default gerrit server definition
     server-name: 'Primary'