OR-486 Remove .skip for Elasticsearch tests
OR-486 Replace mongod replica set check timeout by interval request

* Remove the "exec child process" that did `rs.initiate` and replace it
by using the node mongodb driver.
* Specify the localhost address for `rs.initiate()` in order to fix
problems when user has an exotic network configuration.
Merge pull request #422 in OR/rse from ~RPIGNOLET/rse:OR-486 to master

* commit 'e9f8e3333693e78b4f1643eaa10c9e77d3111bac':
  OR-486 Replace mongod replica set check timeout by interval request
  OR-486 Remove .skip for Elasticsearch tests