Ignore interrupts during quickdie().
Ignore interrupts during quickdie().

Once the administrator has called for an immediate shutdown or a backend
crash has triggered a reinitialization, no mere SIGINT or SIGTERM should
change that course.  Such derailment remains possible when the signal
arrives before quickdie() blocks signals.  That being a narrow race
affecting most PostgreSQL signal handlers in some way, leave it for
another patch.  Back-patch this to all supported versions.

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