Adds MON Prometheus exporter

Adds a new MON component called mon-exporter, which collects
vdu infra metrics and exposes them through a webservice
by using prometheus_client. This webservice follows the Prometheus
exporter format so it can be integrated as a target so that
it polls metrics from there.

Signed-off-by: Benjamin Diaz <bdiaz@whitestack.com>
Change-Id: Iaf2073879d884d0597aa8341f7b6fbbbc3d86e7e
diff --git a/debian/python3-osm-mon.postinst b/debian/python3-osm-mon.postinst
index 3fa26dc..89cd2b3 100644
--- a/debian/python3-osm-mon.postinst
+++ b/debian/python3-osm-mon.postinst
@@ -16,4 +16,5 @@
 pip3 install bottle==0.12.*
 pip3 install peewee==3.1.*
 pip3 install pyyaml==3.*
+pip3 install prometheus_client==0.4.*
 echo "Installation of python dependencies finished"
\ No newline at end of file