Problem:

Suppose there is a foreign key constraint between two tables - from
table t1 (child) to table t2 (parent).  If the loading of t2 passed,
but the loading of table t1 failed, then there was a memory leak
involving the foreign key constraint object in the dictionary cache.

Solution:

Ensure that the foreign key constraint object is always loaded only
along with the child table.  There is no need to load the foreign
key constraint object along with the parent table.

rb#8717 approved by Krunal and Kevin.