r/collectd: Add missing processes.conf template

I forgot to `git add` the template file.

roles/collectd/templates/collectd-processes.conf.j2

@@ -0,0 +1,11 @@
+{% if collectd_processes|d %}
+<Plugin processes>
+{% for proc in collectd_processes %}
+{% if proc.regex is defined %}
+    ProcessMatch "{{ proc.name }}" "{{ proc.regex }}"
+{% else %}
+    Process "{{ proc.name }}"
+{% endif %}
+{% endfor %}
+</Plugin>
+{% endif %}