Increase test coverage in RI_FKey_fk_upd_check_required()
This checks the code path of FKCONSTR_MATCH_FULL and
RI_KEYS_SOME_NULL.
Reviewed-by: Alvaro Herrera <alvherre@2ndquadrant.com>
Reviewed-by: Mi Tar <mmitar@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/
7ae17c95-0c99-d420-032a-
c271f510112b@2ndquadrant.com/