Use a non-locking initial test in TAS_SPIN on PPC.
Use a non-locking initial test in TAS_SPIN on PPC.

Further testing convinces me that this is helpful at sufficiently high
contention levels, though it's still worrisome that it loses slightly
at lower contention levels.

Per Manabu Ori.

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