Update git submodules

* Update docs/submodules/releng/builder from branch 'master'
  to a2cb658c68669e54d08ec48f8447a28c707e4ac2
  - Merge "Update user variables to match common-packer"
  - Update user variables to match common-packer

    common-packer changes some of the variable names in order to
    standardize with all the other clouds managed by LF. Let us update
    the variables to match.

    Change-Id: I7d3783fa728a51c86176a0325d0b69a1e0d9bea5
    Signed-off-by: Thanh Ha <thanh.ha@linuxfoundation.org>

diff --git a/docs/submodules/releng/builder b/docs/submodules/releng/builder
index c43275dfa29e4759c12eb34f0408bd7bb8bc382d..a2cb658c68669e54d08ec48f8447a28c707e4ac2 160000 (submodule)
--- a/docs/submodules/releng/builder
+++ b/docs/submodules/releng/builder
@@ -1 +1 @@
-Subproject commit c43275dfa29e4759c12eb34f0408bd7bb8bc382d
+Subproject commit a2cb658c68669e54d08ec48f8447a28c707e4ac2