Add dependency on "common" role to the elasticsearch role.

The role makes use of some variables from common_vars (notably COMMON_*_DIR), so
it should depend on the "common" role.  With this change applied, it's possible
to run the elasticsearch role using the run_role.yml playbook, which is
sometimes convenient.

playbooks/roles/elasticsearch/meta/main.yml

+---
+dependencies:
+  - common