Add missing CommandCounterIncrement

Add missing CommandCounterIncrement

For commit b663b9436e75 I thought this was useless, but turns out not to
be for the case where a partitioned table has two identical foreign key
constraints which can both be matched by the same constraint in a
partition during attach.  This CCI makes the match search for the second
constraint in the parent ignore the constraint in the child that has
already been matched by the first constraint in the parent.

Reported-by: Alexander Lakhin <exclusion@gmail.com>
Discussion: https://postgr.es/m/c599253c-1ccd-4161-80fc-c9065e037a09@gmail.com