The optimizer chose a less efficient execution plan due to the following
defects of the code:
1. the generic handler function handler::keyread_time did not take into account
   that in clustered primary keys record data is included into each index entry
2. the function make_join_readinfo erroneously decided that index only scan
   could not be used if join cache was empoyed.

Added no additional test case.
Adjusted some of the test results.