Add DISCARD to the command_no_begin list for AUTOCOMMIT=off. Backpatch to 8.3.
Add DISCARD to the command_no_begin list for AUTOCOMMIT=off.
Backpatch to 8.3.

Reported by Sergey Burladyan.

greenplum-db/gpdb,oberstet/postgres-xl,xinzweb/gpdb,adam8157/gpdb,tpostgres-projects/tPostgres,kmjungersen/PostgresXL,lisakowen/gpdb,xinzweb/gpdb,50wu/gpdb,ovr/postgres-xl,jmcatamney/gpdb,greenplum-db/gpdb,jmcatamney/gpdb,greenplum-db/gpdb,kmjungersen/PostgresXL,pavanvd/postgres-xl,ovr/postgres-xl,ovr/postgres-xl,greenplum-db/gpdb,arcivanov/postgres-xl,arcivanov/postgres-xl,ashwinstar/gpdb,zeroae/postgres-xl,zeroae/postgres-xl,tpostgres-projects/tPostgres,adam8157/gpdb,50wu/gpdb,snaga/postgres-xl,kmjungersen/PostgresXL,adam8157/gpdb,xinzweb/gpdb,Postgres-XL/Postgres-XL,tpostgres-projects/tPostgres,jmcatamney/gpdb,jmcatamney/gpdb,lisakowen/gpdb,adam8157/gpdb,pavanvd/postgres-xl,yazun/postgres-xl,tpostgres-projects/tPostgres,jmcatamney/gpdb,techdragon/Postgres-XL,lisakowen/gpdb,greenplum-db/gpdb,xinzweb/gpdb,Postgres-XL/Postgres-XL,xinzweb/gpdb,Postgres-XL/Postgres-XL,ovr/postgres-xl,techdragon/Postgres-XL,arcivanov/postgres-xl,tpostgres-projects/tPostgres,ashwinstar/gpdb,postmind-net/postgres-xl,greenplum-db/gpdb,jmcatamney/gpdb,pavanvd/postgres-xl,yazun/postgres-xl,zeroae/postgres-xl,xinzweb/gpdb,snaga/postgres-xl,arcivanov/postgres-xl,zeroae/postgres-xl,kmjungersen/PostgresXL,lisakowen/gpdb,lisakowen/gpdb,snaga/postgres-xl,50wu/gpdb,jmcatamney/gpdb,lisakowen/gpdb,snaga/postgres-xl,50wu/gpdb,lisakowen/gpdb,techdragon/Postgres-XL,snaga/postgres-xl,50wu/gpdb,lisakowen/gpdb,postmind-net/postgres-xl,yazun/postgres-xl,adam8157/gpdb,pavanvd/postgres-xl,50wu/gpdb,ashwinstar/gpdb,pavanvd/postgres-xl,oberstet/postgres-xl,ashwinstar/gpdb,postmind-net/postgres-xl,yazun/postgres-xl,oberstet/postgres-xl,xinzweb/gpdb,postmind-net/postgres-xl,50wu/gpdb,techdragon/Postgres-XL,50wu/gpdb,ashwinstar/gpdb,adam8157/gpdb,ashwinstar/gpdb,arcivanov/postgres-xl,adam8157/gpdb,oberstet/postgres-xl,kmjungersen/PostgresXL,xinzweb/gpdb,ovr/postgres-xl,yazun/postgres-xl,postmind-net/postgres-xl,techdragon/Postgres-XL,zeroae/postgres-xl,greenplum-db/gpdb,adam8157/gpdb,ashwinstar/gpdb,oberstet/postgres-xl,greenplum-db/gpdb,Postgres-XL/Postgres-XL,arcivanov/postgres-xl,jmcatamney/gpdb,Postgres-XL/Postgres-XL,ashwinstar/gpdb