moutnroot failing on zpools in Azure after upgrade from 10 to 11 due to lack of waiting for da0

[Julian Elischer]

this was a bug in 10.3 that I thought was fixed in 11.. I believe it's 
fixed in 10-stable. Maybe 11.0 missed it?


if you still see this bug look at adding the patch in bug
    https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=208882

it makes the mountroot code retry, which is all you need.

Julian