Fix UnpackCheckPointRecord Assert failure
Fix UnpackCheckPointRecord Assert failure

During gp_expand, the guc gp_before_filespace_setup is used to skip
mmxlog and ptas information from the checkpoint record. However, the
UnpackCheckPointRecord() was expecting additional information.

The fix is to make that part optional based on the remaining length of
checkpoint record.

Signed-off-by: Xin Zhang <80ac6425c128040c27b3c6077c824bc26222f5e7@pivotal.io>

kaknikhil/gpdb,50wu/gpdb,adam8157/gpdb,cjcjameson/gpdb,greenplum-db/gpdb,cjcjameson/gpdb,cjcjameson/gpdb,yuanzhao/gpdb,ashwinstar/gpdb,ashwinstar/gpdb,jmcatamney/gpdb,cjcjameson/gpdb,jmcatamney/gpdb,cjcjameson/gpdb,greenplum-db/gpdb,xinzweb/gpdb,lisakowen/gpdb,cjcjameson/gpdb,kaknikhil/gpdb,kaknikhil/gpdb,janebeckman/gpdb,lisakowen/gpdb,lisakowen/gpdb,adam8157/gpdb,50wu/gpdb,50wu/gpdb,lisakowen/gpdb,janebeckman/gpdb,Chibin/gpdb,greenplum-db/gpdb,yuanzhao/gpdb,edespino/gpdb,xinzweb/gpdb,yuanzhao/gpdb,yuanzhao/gpdb,cjcjameson/gpdb,lisakowen/gpdb,greenplum-db/gpdb,janebeckman/gpdb,ashwinstar/gpdb,xinzweb/gpdb,jmcatamney/gpdb,Chibin/gpdb,yuanzhao/gpdb,adam8157/gpdb,ashwinstar/gpdb,adam8157/gpdb,edespino/gpdb,kaknikhil/gpdb,janebeckman/gpdb,yuanzhao/gpdb,jmcatamney/gpdb,50wu/gpdb,janebeckman/gpdb,xinzweb/gpdb,ashwinstar/gpdb,Chibin/gpdb,50wu/gpdb,edespino/gpdb,Chibin/gpdb,cjcjameson/gpdb,greenplum-db/gpdb,yuanzhao/gpdb,ashwinstar/gpdb,adam8157/gpdb,edespino/gpdb,greenplum-db/gpdb,Chibin/gpdb,yuanzhao/gpdb,50wu/gpdb,janebeckman/gpdb,Chibin/gpdb,kaknikhil/gpdb,ashwinstar/gpdb,jmcatamney/gpdb,edespino/gpdb,yuanzhao/gpdb,kaknikhil/gpdb,xinzweb/gpdb,kaknikhil/gpdb,edespino/gpdb,jmcatamney/gpdb,xinzweb/gpdb,50wu/gpdb,ashwinstar/gpdb,adam8157/gpdb,kaknikhil/gpdb,edespino/gpdb,Chibin/gpdb,jmcatamney/gpdb,lisakowen/gpdb,xinzweb/gpdb,lisakowen/gpdb,edespino/gpdb,adam8157/gpdb,janebeckman/gpdb,greenplum-db/gpdb,cjcjameson/gpdb,Chibin/gpdb,greenplum-db/gpdb,Chibin/gpdb,edespino/gpdb,Chibin/gpdb,yuanzhao/gpdb,kaknikhil/gpdb,xinzweb/gpdb,50wu/gpdb,janebeckman/gpdb,edespino/gpdb,kaknikhil/gpdb,adam8157/gpdb,janebeckman/gpdb,cjcjameson/gpdb,jmcatamney/gpdb,janebeckman/gpdb,lisakowen/gpdb