CI: Update common-packer to the latest v0.7.7

Change-Id: I19251c9e00e38fa1965d55e585271e1e4d622cf1
Issue-ID: CIMAN-33
Signed-off-by: Anil Belur <abelur@linuxfoundation.org>

diff --git a/packer/common-packer b/packer/common-packer
index 74b6be7..3494343 160000 (submodule)
--- a/packer/common-packer
+++ b/packer/common-packer
@@ -1 +1 @@
-Subproject commit 74b6be7301b5c407d1ccf4cf6093b3b8cd308ad7
+Subproject commit 3494343faf0fc4221bfdb6cefc8bc0af0452f980