get_control_data: fix checksum version check
get_control_data: fix checksum version check

Follow-up to 71916050. Checksums were backported to Postgres 8.3, so we
ignore them for <= 8.2.

While we're at it, switch the data_checksum_version from a false
assignment to a zero assignment, to match upstream. The actual
implementation is an unsigned int; Postgres master incorrectly uses a
bool type in the declaration.

50wu/gpdb,50wu/gpdb,ashwinstar/gpdb,50wu/gpdb,jmcatamney/gpdb,greenplum-db/gpdb,xinzweb/gpdb,jmcatamney/gpdb,50wu/gpdb,adam8157/gpdb,jmcatamney/gpdb,jmcatamney/gpdb,ashwinstar/gpdb,xinzweb/gpdb,greenplum-db/gpdb,xinzweb/gpdb,ashwinstar/gpdb,lisakowen/gpdb,adam8157/gpdb,50wu/gpdb,greenplum-db/gpdb,ashwinstar/gpdb,lisakowen/gpdb,jmcatamney/gpdb,50wu/gpdb,xinzweb/gpdb,50wu/gpdb,ashwinstar/gpdb,greenplum-db/gpdb,jmcatamney/gpdb,xinzweb/gpdb,lisakowen/gpdb,adam8157/gpdb,adam8157/gpdb,ashwinstar/gpdb,greenplum-db/gpdb,xinzweb/gpdb,lisakowen/gpdb,adam8157/gpdb,jmcatamney/gpdb,xinzweb/gpdb,greenplum-db/gpdb,greenplum-db/gpdb,50wu/gpdb,ashwinstar/gpdb,jmcatamney/gpdb,adam8157/gpdb,ashwinstar/gpdb,lisakowen/gpdb,lisakowen/gpdb,adam8157/gpdb,lisakowen/gpdb,greenplum-db/gpdb,adam8157/gpdb,lisakowen/gpdb,xinzweb/gpdb