Allow to use drop-slot-on-close option with wal2json

The drop-slot-on-close option for Postgres is implemented via temporary replication slots when using PG 10 or newer (see DBZ-934). That slot is dropped when failing to establish the replication stream with non-existent wal2json options. So the slot should be re-established in that case.

Also let's

• add the combinatation of wal2json and PG 10 to the matrix testing job: http://ci.hibernate.org/view/Debezium/job/debezium-postgresql-matrix-test/
• see why there are that many yellow ones in that job