Two source-and-replica pairs run in containers: one replicating with
GTIDs, one by binary log position. mysql_replica_tests covers test 17
(tests 9, 10 and 12 with GTIDs) and mysql_replica_position_tests covers
test 18 (lag from Seconds_Behind_Source, and a replica whose account
lacks REPLICATION CLIENT getting no reads) and test 19 (a parallel
replica without replica_preserve_commit_order left out at startup).
The lag reader now takes Seconds_Behind_Source whatever numeric type the
server returns, accepts the older column name, and says in the log why it
gave up measuring.
jcoffey-dev
e913a22b66