Make code for selecting default WAL sync method less confusing.
Make code for selecting default WAL sync method less confusing.

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