Fix fuzzy thinking in ReinitializeParallelDSM().
Fix fuzzy thinking in ReinitializeParallelDSM().

The fact that no workers were successfully launched in the previous
iteration does not excuse us from setting up properly to try again.
This appears to explain crashes I saw in parallel regression testing
due to error_mqh being NULL when it shouldn't be.

Minor other cosmetic fixes too.

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