Add some elog(DEBUG)'s to help diagnose mdblindwrt failures.
Add some elog(DEBUG)'s to help diagnose mdblindwrt failures.

edespino/gpdb,yuanzhao/gpdb,xinzweb/gpdb,xinzweb/gpdb,postmind-net/postgres-xl,snaga/postgres-xl,janebeckman/gpdb,snaga/postgres-xl,adam8157/gpdb,jmcatamney/gpdb,tangp3/gpdb,lintzc/gpdb,Postgres-XL/Postgres-XL,rubikloud/gpdb,Chibin/gpdb,yuanzhao/gpdb,zaksoup/gpdb,foyzur/gpdb,xinzweb/gpdb,janebeckman/gpdb,oberstet/postgres-xl,atris/gpdb,Chibin/gpdb,Chibin/gpdb,cjcjameson/gpdb,greenplum-db/gpdb,lpetrov-pivotal/gpdb,lpetrov-pivotal/gpdb,rvs/gpdb,rvs/gpdb,edespino/gpdb,rubikloud/gpdb,postmind-net/postgres-xl,pavanvd/postgres-xl,adam8157/gpdb,lisakowen/gpdb,Quikling/gpdb,arcivanov/postgres-xl,Chibin/gpdb,Chibin/gpdb,0x0FFF/gpdb,jmcatamney/gpdb,rubikloud/gpdb,ahachete/gpdb,kaknikhil/gpdb,0x0FFF/gpdb,janebeckman/gpdb,techdragon/Postgres-XL,Postgres-XL/Postgres-XL,rvs/gpdb,tangp3/gpdb,ovr/postgres-xl,ashwinstar/gpdb,greenplum-db/gpdb,greenplum-db/gpdb,techdragon/Postgres-XL,janebeckman/gpdb,Quikling/gpdb,arcivanov/postgres-xl,rubikloud/gpdb,lintzc/gpdb,atris/gpdb,greenplum-db/gpdb,50wu/gpdb,randomtask1155/gpdb,janebeckman/gpdb,oberstet/postgres-xl,0x0FFF/gpdb,kaknikhil/gpdb,Quikling/gpdb,ovr/postgres-xl,pavanvd/postgres-xl,xuegang/gpdb,xinzweb/gpdb,ashwinstar/gpdb,edespino/gpdb,CraigHarris/gpdb,Quikling/gpdb,xuegang/gpdb,edespino/gpdb,xuegang/gpdb,foyzur/gpdb,adam8157/gpdb,lisakowen/gpdb,edespino/gpdb,greenplum-db/gpdb,cjcjameson/gpdb,arcivanov/postgres-xl,50wu/gpdb,zeroae/postgres-xl,lintzc/gpdb,0x0FFF/gpdb,chrishajas/gpdb,jmcatamney/gpdb,rubikloud/gpdb,chrishajas/gpdb,lpetrov-pivotal/gpdb,lintzc/gpdb,cjcjameson/gpdb,kaknikhil/gpdb,lisakowen/gpdb,lintzc/gpdb,foyzur/gpdb,CraigHarris/gpdb,yazun/postgres-xl,kaknikhil/gpdb,tangp3/gpdb,yuanzhao/gpdb,techdragon/Postgres-XL,oberstet/postgres-xl,janebeckman/gpdb,janebeckman/gpdb,yazun/postgres-xl,rvs/gpdb,cjcjameson/gpdb,foyzur/gpdb,foyzur/gpdb,adam8157/gpdb,zeroae/postgres-xl,postmind-net/postgres-xl,kaknikhil/gpdb,janebeckman/gpdb,zaksoup/gpdb,ahachete/gpdb,yuanzhao/gpdb,zeroae/postgres-xl,atris/gpdb,ahachete/gpdb,cjcjameson/gpdb,atris/gpdb,xuegang/gpdb,lintzc/gpdb,CraigHarris/gpdb,yuanzhao/gpdb,lisakowen/gpdb,rvs/gpdb,50wu/gpdb,Postgres-XL/Postgres-XL,0x0FFF/gpdb,pavanvd/postgres-xl,kmjungersen/PostgresXL,zaksoup/gpdb,royc1/gpdb,ashwinstar/gpdb,oberstet/postgres-xl,kmjungersen/PostgresXL,ahachete/gpdb,lpetrov-pivotal/gpdb,Quikling/gpdb,adam8157/gpdb,kaknikhil/gpdb,Chibin/gpdb,royc1/gpdb,Postgres-XL/Postgres-XL,janebeckman/gpdb,lisakowen/gpdb,CraigHarris/gpdb,edespino/gpdb,cjcjameson/gpdb,zaksoup/gpdb,50wu/gpdb,yuanzhao/gpdb,greenplum-db/gpdb,xinzweb/gpdb,adam8157/gpdb,rvs/gpdb,randomtask1155/gpdb,zaksoup/gpdb,50wu/gpdb,zaksoup/gpdb,50wu/gpdb,ahachete/gpdb,chrishajas/gpdb,tpostgres-projects/tPostgres,lisakowen/gpdb,randomtask1155/gpdb,rubikloud/gpdb,ahachete/gpdb,janebeckman/gpdb,Chibin/gpdb,royc1/gpdb,xuegang/gpdb,edespino/gpdb,tpostgres-projects/tPostgres,kaknikhil/gpdb,randomtask1155/gpdb,ahachete/gpdb,kaknikhil/gpdb,yuanzhao/gpdb,kaknikhil/gpdb,0x0FFF/gpdb,yazun/postgres-xl,xinzweb/gpdb,snaga/postgres-xl,kmjungersen/PostgresXL,edespino/gpdb,yuanzhao/gpdb,kaknikhil/gpdb,Quikling/gpdb,rvs/gpdb,tpostgres-projects/tPostgres,tpostgres-projects/tPostgres,xuegang/gpdb,royc1/gpdb,chrishajas/gpdb,postmind-net/postgres-xl,Postgres-XL/Postgres-XL,ovr/postgres-xl,Quikling/gpdb,CraigHarris/gpdb,lpetrov-pivotal/gpdb,zeroae/postgres-xl,postmind-net/postgres-xl,cjcjameson/gpdb,xuegang/gpdb,atris/gpdb,foyzur/gpdb,yuanzhao/gpdb,Quikling/gpdb,adam8157/gpdb,oberstet/postgres-xl,foyzur/gpdb,zeroae/postgres-xl,royc1/gpdb,50wu/gpdb,rvs/gpdb,atris/gpdb,adam8157/gpdb,pavanvd/postgres-xl,0x0FFF/gpdb,lpetrov-pivotal/gpdb,50wu/gpdb,edespino/gpdb,lisakowen/gpdb,randomtask1155/gpdb,cjcjameson/gpdb,royc1/gpdb,yazun/postgres-xl,rubikloud/gpdb,ahachete/gpdb,cjcjameson/gpdb,chrishajas/gpdb,CraigHarris/gpdb,tangp3/gpdb,tangp3/gpdb,lisakowen/gpdb,chrishajas/gpdb,ashwinstar/gpdb,rvs/gpdb,ovr/postgres-xl,jmcatamney/gpdb,arcivanov/postgres-xl,CraigHarris/gpdb,jmcatamney/gpdb,ashwinstar/gpdb,Quikling/gpdb,lintzc/gpdb,royc1/gpdb,Quikling/gpdb,zaksoup/gpdb,Chibin/gpdb,lpetrov-pivotal/gpdb,arcivanov/postgres-xl,kmjungersen/PostgresXL,chrishajas/gpdb,tangp3/gpdb,ovr/postgres-xl,randomtask1155/gpdb,xinzweb/gpdb,chrishajas/gpdb,jmcatamney/gpdb,yuanzhao/gpdb,ashwinstar/gpdb,foyzur/gpdb,yazun/postgres-xl,xuegang/gpdb,rvs/gpdb,Chibin/gpdb,greenplum-db/gpdb,pavanvd/postgres-xl,lpetrov-pivotal/gpdb,Chibin/gpdb,ashwinstar/gpdb,0x0FFF/gpdb,xinzweb/gpdb,techdragon/Postgres-XL,lintzc/gpdb,jmcatamney/gpdb,snaga/postgres-xl,CraigHarris/gpdb,snaga/postgres-xl,cjcjameson/gpdb,CraigHarris/gpdb,tangp3/gpdb,royc1/gpdb,atris/gpdb,greenplum-db/gpdb,rubikloud/gpdb,randomtask1155/gpdb,edespino/gpdb,tangp3/gpdb,randomtask1155/gpdb,zaksoup/gpdb,ashwinstar/gpdb,xuegang/gpdb,kmjungersen/PostgresXL,atris/gpdb,tpostgres-projects/tPostgres,arcivanov/postgres-xl,jmcatamney/gpdb,lintzc/gpdb,techdragon/Postgres-XL