MFC r249328:

Make ctladm(8) try to load ctl.ko kernel module if needed.

Approved by:	re (delphij)
Revert r249530 and re-enable compilation of ctl.ko for all configurations
except i386 XEN, for which it still doesn't build so far.
This is a direct commit to stable/9.

Approved by:	re (delphij, kib)
Merge remote-tracking branch 'upstream-github/stable/9' into stable/9