krpc: unbootable ZFS-on-root after major upgrade to 11.2

[Eugene Grosbein]

Hi!

It was brought to my attention that 10.x did not require availability
of krpc for ZFS-on-root system to be bootable but 11.x does.

That is, major upgrade of 10.x ZFS-on-root system to 11.x
results in non-bootable broken system if it uses custom kernel without NFS bits
that automatically come with krpc, and the system was built with MODULES_OVERRIDE="zfs opensolaris"
and no krpc mentioned.

We could have mentioned that requrement in Release Notes but we had not.

Should we issue an Errata Note?