Fix test failures

Use larger BLOB type for mxs812_1, the inserted value exceeds the normal
BLOB size.

Add a baseline check into bulk_insert to verify that direct connections
work (at the moment they don't, needs an investigation).

Updated parameter names in failover_mysqlmon_mrm.

Modified avro_alter to prevent data type conversion errors.

maxscale-system-test/cnf/maxscale.cnf.template.failover_mysqlmon_mrm

@@ -11,7 +11,7 @@ monitor_interval=1000
 detect_standalone_master=true
 failcount=1
 allow_cluster_recovery=true
-failover=true
+auto_failover=true
 replication_user=repl
 replication_password=repl
 backend_connect_timeout=1