[SRU xenial/zesty/arful/bionic] LP#1737176: Disable zfs modules checks any time zfs is disabled

[Andy Whitcroft]

Disabling zfs does not always disable module checks for the zfs modules.
We do disable them when we disable zfs as part of a cross-compile.  We
should also disable them when we are specifically turning zfs off for
any other reason including when passed in manually.

Proposing for SRU to anything with ZFS applied which is everything from
xenial upwards.

-apw