Process the Disk table ordered by enabled disks

This will prevent disabled disks of same name being bring back to life,
causing all sorts of problem like blank serial numbers.

Ticket:	#4366
(cherry picked from commit e245274a46f5dcb9a803fd4e157c0e946c732394)
Add is_freenas function to check if we are FreeNAS or TrueNAS
Use syslog dataset only for FreeNAS

Ticket:	#4391
Add done method and hook for normal forms
Use done method for VolumeManagerForm

This is allow hook for it as well.

Ticket:	#4407
Fix API breakage introduced in 9e2a5306f14

Now heading to the beach for carnival! :)

Ticket:	#4420