Make opendmarc database setup more robust

Instead of registering a handler to run when the database is created,
register a variable and check it immediately to run the schema import.
This avoids a problem where an error between database creation and
schema import 1) leaves the server in a broken state, and 2) rerunning
the playbook doesn't fix it.

roles/mailserver/handlers/main.yml

 
 - name: restart rspamd
   service: name=rspamd state=restarted
-
-- name: import opendmarc schema
-  mysql_db: name={{ mail_db_opendmarc_database }} state=import target=/usr/share/doc/opendmarc/schema.mysql

roles/mailserver/tasks/opendmarc.yml

 
 - name: Create database for OpenDMARC reports
   mysql_db: name={{ mail_db_opendmarc_database }} state=present
-  notify: import opendmarc schema
+  register: db_created
+
+- name: Import opendmarc schema
+  mysql_db: name={{ mail_db_opendmarc_database }} state=import target=/usr/share/doc/opendmarc/schema.mysql
+  when: db_created.changed
 
 - name: Copy nightly OpenDMARC report generation script into place
   template: src=etc_opendmarc_report.sh.j2 dest=/etc/opendmarc/report.sh owner=root group=root mode="755"