Stricter order for actor.org_unit_parent_protect()

Stricter order for actor.org_unit_parent_protect()

actor.org_unit_parent_protect() may not work due to the fact
that 'IF' conditions in PL/pgSQL are not necessarily processed
in the order written. This line:

"IF TG_OP = 'INSERT' OR NEW.parent_ou
IS DISTINCT FROM OLD.parent_ou THEN"

may fail because the 'IS DISTINCT FROM' happens before the
'INSERT' check, and and that fails because there is no 'OLD'
variable for INSERTs.

This commit may not be the optimal style for this circumstance
in this language, but it works.  It also appears to change more
than it really does due to a loss of one level of indentation in
the structure.

Signed-off-by: Dan Wells <dbw2@calvin.edu>