Add support for running multiple LDAP servers

The ldap-test-server-py4j java server now provides support for running multiple LDAP servers at the same time, so lets take advantage of that so we perform tests that may require more than one LDAP server.

This patch requires an updated version of ldap-test-server-py4j that includes the pull request: https://github.com/zoldar/ldap-test-server-py4j/pull/1