Metadata issues with CHECK TABLE/PARTITION before starting load

The work on PSTRESS-132 led to the discovery of some unnoticed issues with the metadata before starting the load for each step/trial.

When CHECK TABLE/PARTITION queries were added before, a small(~5%) percentage of such queries failed because of one of the following reasons. They need to be investigated and fixed if they turn out be critical.

1. Table doesn't exist error.

2. Partition doesn't exist error.

3. Deadlock found when trying to get lock error.

The issues can be reproduced just by looking at the thread logs once the patch for PSTRESS-132 is pushed. But, if pstress needs to be aborted, a hard return false can be added at the error paths of method, bool check_tables_partitions_preload(Thd1 *thd) {}{}.