Change disable/enable flags to booleans.
+ module_param() requires the variable to be defined as a 'true/false'
  value, not '0/1' therefor create a separate type 'bool' with this.
+ This require https://github.com/zfsonlinux/zfs/pull/1993 to be applied first
  since that created the 'bool' false/true enum that this patch uses.