[TEST] Expose `tests.filter` for elasticsearch tests.

`-Dtests.filter` allows to pass filter expressions to the elasticsearch
tests. This allows to filter test annotaged with TestGroup annotations
like @Slow, @Nightly, @Backwards, @Integration with a boolean expresssion like:

 * to run only backwards tests run:
     `mvn -Dtests.bwc.version=X.Y.Z -Dtests.filter="@backwards"`
 * to run all integration tests but skip slow tests run:
     `mvn -Dtests.filter="@integration and not @slow"
 * to take defaults into account ie run all test as well as backwards:
     `mvn -Dtests.filter="default and @backwards"

This feature is a more powerful alternative to flags like
`-Dtests.nighly=true|false` etc.