Allow to run tests in Docker

* Adapted tests/test_playbook_runs.py script to allow tests to be
  executed from a docker container.
* Added molecule scenarios to create/destroy test containers and
  respective documentation in tests/README.md.

molecule/resources/playbooks/prepare.yml

@@ -0,0 +1,18 @@
+---
+- name: Converge
+  hosts: all
+  tasks:
+  - name: Ensure lock dirs for DS exists
+    file:
+      state: directory
+      owner: dirsrv
+      group: dirsrv
+      path: "{{ item }} "
+    loop:
+      - /var/lock/dirsrv/
+      - /var/lock/dirsrv/slapd-TEST-LOCAL/
+
+  - name: Ensure IPA server is up an running
+    service:
+      name: ipa
+      state: started