Fix failure to enforce partitioning contraint for internal partitions.

Fix failure to enforce partitioning contraint for internal partitions.

When a tuple is inherited into a partitioning root, no partition
constraints need to be enforced; when it is inserted into a leaf, the
parent's partitioning quals needed to be enforced.  The previous
coding got both of those cases right.  When a tuple is inserted into
an intermediate level of the partitioning hierarchy (i.e. a table
which is both a partition itself and in turn partitioned), it must
enforce the partitioning qual inherited from its parent.  That case
got overlooked; repair.

Amit Langote