Fix for failing testcase inherit.sql. It has following changes
1. Added ORDER BY clause to make sure that the query result is always the same.
2. The test uses temporary objects which do not work with 2PC in PostgreSQL.
   Used GUC to allow using 2PC with temporary objects.
3. Updated the original expected output file with the changed plans in XC.
Fix for failing testcase truncate.sql.
1. Used replicated tables, which were referenced by other tables and the primary
keys and foreign keys couldn't reside on same node, if the table would have been
distributed.
2. Triggers are now supported. Corrected the expected output in alternate output
file accordingly.