Move test.default.yaml over to 6.4

(cherry picked from commit 63edd99)

Author: Mpdreamz

src/Tests/Tests.Configuration/tests.default.yaml

@@ -8,7 +8,7 @@
 mode: u
 # the elasticsearch version that should be started
 # Can be a snapshot version of sonatype or "latest" to get the latest snapshot of sonatype
-elasticsearch_version: 6.3.0
+elasticsearch_version: 6.4.1
 # cluster filter allows you to only run the integration tests of a particular cluster (cluster suffix not needed)
 # cluster_filter:
 # whether we want to forcefully reseed on the node, if you are starting the tests with a node already running