update rel/fk FAQ entry

update rel/fk FAQ entry

this entry still made the assumptions of behavior before
ticket #3061, that accessing a non-initialized scalar attribute
on a pending object would populate the attribute with None.
It also used the word "initialize" when referring to a persistent
object which is a misleading term, it's "loaded", even though
in this example it's "loading" the value of None.

Fix up the language to be more consistent with the #3061 change.

Change-Id: I1abd8f1d2e9c44ebc9a29737ea270b338f104a3e