Do reindexing concurrently

Now that we're not doing the reindexing in single user mode, we'd
better to it concurrently so as to avoid blocking (as much) for
larger sized databases

pgautoupgrade-postupgrade.sh

@@ -32,7 +32,7 @@ for DATABASE in ${DB_LIST}; do
  echo "Starting reindex of ${DATABASE}"
  echo "-------------------------------"
 
- echo 'REINDEX DATABASE' | psql -t --csv "${DATABASE}"
+ echo 'REINDEX DATABASE CONCURRENTLY' | psql -t --csv "${DATABASE}"
 
  echo "-------------------------------"
  echo "Finished reindex of ${DATABASE}"