On Windows with low precision (10-16 ms) timer used for timing queries,
the statement "set @@long_query_time=0.01" can log itself a slow if it
spawn more single timer tick.
The fix is to filter this query out from "SELECT FROM mysql.slow_log"
results
fixed embedded server tests
MDEV-7009: SET STATEMENT min_examined_row_limit has no effect
MDEV-6948:SET STATEMENT gtid_domain_id = ... FOR has no effect (same for gtid_seq_no and server_id)
old values of SET STATENENT variables now saved in its own Query_arena and restored later