For HasId.setRef, have first set win (with force override) (#1655) (#1657)

This is a refinement of the assertion added in #1616 then removed in
 #1654. Because Records now set the refs of children upon binding,
later, unbound Records could incorrectly override the refs. The first
set should win.

(cherry picked from commit 8187318e

)

Co-authored-by: Jack Koenig <koenig@sifive.com>