Update the mongo-java-driver to 2.13.0-rc0

This release contains a bunch of improvements and bug fixes, in particular:
* [JAVA-1472]: #equals()/#hashCode() for MongoClientURI
* [JAVA-1519]: DBCursor finalizer no longer holds on to the query results
* [JAVA-591] : Potential OOM with long-running tailable cursors
Disable tracking of the batch sizes received by the cursor

Relates-to: https://jira.mongodb.org/browse/JAVA-591
Merge branch 'driver-2.13.0-rc0' into master-collaborne

Conflicts:
	src/main/java/org/elasticsearch/river/mongodb/OplogSlurper.java