meta-phosphor: prep for new override syntax

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I588025b614416c43aa2d053765ab53bacf890cb5
diff --git a/meta-phosphor/conf/local.conf.sample b/meta-phosphor/conf/local.conf.sample
index 0a62163..a385367 100644
--- a/meta-phosphor/conf/local.conf.sample
+++ b/meta-phosphor/conf/local.conf.sample
@@ -1,11 +1,11 @@
 MACHINE ??= "qemuarm"
 DISTRO ?= "openbmc-phosphor"
 PACKAGE_CLASSES ?= "package_rpm"
-SANITY_TESTED_DISTROS_append ?= " *"
-EXTRA_IMAGE_FEATURES = "debug-tweaks"
-USER_CLASSES ?= "buildstats image-prelink"
+SANITY_TESTED_DISTROS:append ?= " *"
+EXTRA_IMAGE_FEATURES ?= "debug-tweaks"
+USER_CLASSES ?= "buildstats"
 PATCHRESOLVE = "noop"
-BB_DISKMON_DIRS = "\
+BB_DISKMON_DIRS ??= "\
     STOPTASKS,${TMPDIR},1G,100K \
     STOPTASKS,${DL_DIR},1G,100K \
     STOPTASKS,${SSTATE_DIR},1G,100K \