Remove ill-advised pre-check for DSM segment exhaustion.
Remove ill-advised pre-check for DSM segment exhaustion.

dsm_control->nitems never decreases, so this is testing whether the
server has *ever* run out of DSM segments, not whether it is
*currently* out of DSM segments.

Reported off-list by Amit Kapila.

techdragon/Postgres-XL,adam8157/gpdb,Postgres-XL/Postgres-XL,oberstet/postgres-xl,xinzweb/gpdb,lisakowen/gpdb,ovr/postgres-xl,lisakowen/gpdb,xinzweb/gpdb,techdragon/Postgres-XL,50wu/gpdb,ashwinstar/gpdb,50wu/gpdb,adam8157/gpdb,lisakowen/gpdb,zeroae/postgres-xl,pavanvd/postgres-xl,50wu/gpdb,ashwinstar/gpdb,adam8157/gpdb,ashwinstar/gpdb,techdragon/Postgres-XL,adam8157/gpdb,pavanvd/postgres-xl,jmcatamney/gpdb,oberstet/postgres-xl,xinzweb/gpdb,ashwinstar/gpdb,ovr/postgres-xl,adam8157/gpdb,yazun/postgres-xl,xinzweb/gpdb,jmcatamney/gpdb,xinzweb/gpdb,pavanvd/postgres-xl,50wu/gpdb,zeroae/postgres-xl,yazun/postgres-xl,Postgres-XL/Postgres-XL,jmcatamney/gpdb,lisakowen/gpdb,jmcatamney/gpdb,lisakowen/gpdb,xinzweb/gpdb,lisakowen/gpdb,greenplum-db/gpdb,pavanvd/postgres-xl,oberstet/postgres-xl,lisakowen/gpdb,zeroae/postgres-xl,adam8157/gpdb,xinzweb/gpdb,adam8157/gpdb,ashwinstar/gpdb,adam8157/gpdb,zeroae/postgres-xl,ashwinstar/gpdb,jmcatamney/gpdb,greenplum-db/gpdb,greenplum-db/gpdb,ashwinstar/gpdb,greenplum-db/gpdb,Postgres-XL/Postgres-XL,greenplum-db/gpdb,techdragon/Postgres-XL,jmcatamney/gpdb,pavanvd/postgres-xl,50wu/gpdb,yazun/postgres-xl,oberstet/postgres-xl,oberstet/postgres-xl,ovr/postgres-xl,lisakowen/gpdb,greenplum-db/gpdb,Postgres-XL/Postgres-XL,Postgres-XL/Postgres-XL,jmcatamney/gpdb,greenplum-db/gpdb,ashwinstar/gpdb,greenplum-db/gpdb,50wu/gpdb,xinzweb/gpdb,50wu/gpdb,zeroae/postgres-xl,ovr/postgres-xl,yazun/postgres-xl,ovr/postgres-xl,techdragon/Postgres-XL,yazun/postgres-xl,jmcatamney/gpdb,50wu/gpdb