add back empty whitelist

the log checker fails without a whitelist file, add this back in

Change-Id: I26f0e9789b167061e2a7dac4dddf04d89bfadee3
diff --git a/etc/whitelist.yaml b/etc/whitelist.yaml
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/etc/whitelist.yaml