Clarify 'cert' authentication documention.
Clarify 'cert' authentication documention.

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