Apply path generation for superclasses to Load._set_path_strategy()

Apply path generation for superclasses to Load._set_path_strategy()

Extended the fix first made as part of :ticket:`3287`, where a loader option
made against a subclass using a wildcard would extend itself to include
application of the wildcard to attributes on the super classes as well, to a
"bound" loader option as well, e.g. in an expression like
``Load(SomeSubClass).load_only('foo')``.  Columns that are part of the
parent class of ``SomeSubClass`` will also be excluded in the same way as if
the unbound option ``load_only('foo')`` were used.

Fixes: #4373
Change-Id: I2eee0e587c34323a77df077b9cb699da370c403d