d/changelog: refresh for 0.0.8-3

New release of the package.

Change-Id: I7c1ddc2d7cca729fcb2c45fc111378447d74b349
Git-Dch: Ignore
Signed-off-by: Arturo Borrero Gonzalez <aborrero@wikimedia.org>

debian/changelog

+prometheus-openstack-exporter (0.0.8-3) jessie-wikimedia; urgency=medium
+
+  * [fcbe41f] d/dirs: include /var/cache/prometheus-openstack-exporter
+
+ -- Arturo Borrero Gonzalez <aborrero@wikimedia.org>  Mon, 01 Oct 2018 13:50:06 +0200
+
 prometheus-openstack-exporter (0.0.8-2) jessie-wikimedia; urgency=medium
 
   * [1604501] d/service: fix templates leftovers