Add fsync tests:
Add fsync tests:

	Compare fsync before and after write's close:
	Compare one o_sync write to two:
	Compare file sync methods with one 8k write:
	Compare file sync methods with 2 8k writes:

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