Remove zerodisk from mcp offline image build

We don't need to extend image file and truncate it later
(it consumes extra 40 GB of jenkins slave for nothing)

Closes-bug: PROD-35231
Change-Id: Ia8b9290a936ce36be3033a98742cc6ffb34b8c0a
diff --git a/day01-image/scripts/flush_disk.sh b/day01-image/scripts/flush_disk.sh
new file mode 100644
index 0000000..5d57919
--- /dev/null
+++ b/day01-image/scripts/flush_disk.sh
@@ -0,0 +1,5 @@
+#!/bin/bash
+set -x
+
+echo 3 > /proc/sys/vm/drop_caches
+sync