Downgrade the kernel.

Between 4.14.35 and 4.14.36 some patches were introduced
which slow down image load/pull times considerably.

For now force downgrade the kernel

See: linuxkit/linuxkit#3120

Signed-off-by: Rolf Neugebauer <rolf.neugebauer@docker.com>

lcow.yml

@@ -1,5 +1,6 @@
 kernel:
-  image: linuxkit/kernel:4.14.53
+  # For now use an older kernel. See https://github.com/linuxkit/linuxkit/issues/3120
+  image: linuxkit/kernel:4.14.35
   cmdline: "console=ttyS0"
   tar: none
 init: