During slow execution, e.g. under valgrind, there was a chance
that Aria checkpoint would happen while P_S tables were being
queried; it could cause different data in joined P_S, and
thus combinations of results that the test did not expect.
Fixed by disabling Aria checkpoints for the test.
Before this fix, the performance schema tables were defined in UPPERCASE.
This was incompatible with the lowercase_table_names option, and caused
issues with the install / upgrade process, when changing the lower case
table names setting *after* the install or upgrade.
With this fix, all performance schema tables are exposed with lowercase names.
As a result, the name of the performance schema table is always lowercase,
no matter how / if / when the lowercase_table_names setting if changed.
