Replace GrantObjectType with ObjectType

Replace GrantObjectType with ObjectType

There used to be a lot of different *Type and *Kind symbol groups to
address objects within different commands, most of which have been
replaced by ObjectType, starting with
b256f2426433c56b4bea3a8102757749885b81ba.  But this conversion was never
done for the ACL commands until now.

This change ends up being just a plain replacement of the types and
symbols, without any code restructuring needed, except deleting some now
redundant code.

Reviewed-by: Michael Paquier <michael.paquier@gmail.com>
Reviewed-by: Stephen Frost <sfrost@snowman.net>