Adding persistance to Prometheus

Change-Id: I8467174ac3313f6939a3796499b22845f2910f54
Signed-off-by: lavado <glavado@whitestack.com>
diff --git a/installers/docker/docker-compose.yaml b/installers/docker/docker-compose.yaml
index ab44917..29b7857 100644
--- a/installers/docker/docker-compose.yaml
+++ b/installers/docker/docker-compose.yaml
@@ -6,6 +6,7 @@
   pol_db:
   osm_packages:
   keystone_db:
+  prom_db:
 networks:
   netOSM:
     external:
@@ -54,6 +55,7 @@
       - "${OSM_PROM_PORTS:-9091:9090}"
     volumes:
       - ./prometheus.yml:/etc/prometheus/prometheus.yml:ro
+      - prom_db:/prometheus
     networks:
       - netOSM
   keystone-db: