meta-ibm: prep for new override syntax

Change-Id: I9116ed7260e369136acb39eec15075db2d4dbeba
Signed-off-by: Adriana Kobylak <anoo@us.ibm.com>
diff --git a/meta-ibm/conf/local.conf.sample b/meta-ibm/conf/local.conf.sample
index 0166b95..9680cf0 100644
--- a/meta-ibm/conf/local.conf.sample
+++ b/meta-ibm/conf/local.conf.sample
@@ -4,7 +4,7 @@
 MACHINE ??= "witherspoon"
 DISTRO ?= "openbmc-openpower"
 PACKAGE_CLASSES ?= "package_rpm"
-SANITY_TESTED_DISTROS_append ?= " *"
+SANITY_TESTED_DISTROS:append ?= " *"
 EXTRA_IMAGE_FEATURES = "debug-tweaks"
 USER_CLASSES ?= "buildstats image-prelink"
 PATCHRESOLVE = "noop"