LXC Alpine Mini Root Filesystem networking

Using the mini root filesystem for a Linux container, I have to add bootmisc manually (in addition to networking) to the boot run level. It took some time to figure this out and wish it was either scripted or at least clearly documented.

Specifically, after installing openrc, rebooting, and adding networking to the boot run level via:

`rc-update add networking boot`

the interface won't be brought up automatically unless the interface is brought down before poweroff/reboot (via `ifdown eth0`)

Got around this by adding bootmisc to the boot run level:

`rc-update add bootmisc boot`

Now interfaces come up upon reboot/poweroff regardless of its status when shutting down.

Not sure if it's a bug but for basic networking, this should be more clearly documented and a suggested enhancement.