FIX: DIND

[briceburg]

• Load DIND based on the RUN_DOCKERD environment variable. Previously it would never start due to static string comparisson (the value of variable was never interpolated).
• Include kmod to allow the modprobe command to load iptables when starting dockerd. Previously the modprobe command was unavailable.
  • adds support for DIND in cases where the host's kernel does not have iptables loaded. Requires the SYS_MODULE capability