Add gpreload behave test

* gpreloaqd test where a table (public.t1) and
  view (gpreload_schema.t1) have the same name.

Add gpreload CI test jobs.
Co-authored-by: NEd Espino <eespino@vmware.com>

The maintained tests for gpload are located in gpMgmt/bin/gpload_test.
Authored-by: NChris Hajas <chajas@pivotal.io>

* Enable to run behave tests with the installed binary instead of source
* code.

* This is an effort to enable us to run behave tests without relying on
* the source code and instead use the GPDB installed in the system as
* the behave tests are integration tests.