This adds authentication to Prometheus with an apache reverse
proxy, similar to elasticsearch, kibana and nagios. This adds an
admin user and password via htpasswd along with adding ldap
support.
This required modifying the grafana chart to configure the
prometheus datasource's basic auth credentials in the data sources
provisioning configuration file by checking whether basic auth is
enabled and injecting the username/password defined in the
corresponding endpoint definition.
This also modifies the nagios chart to use the authenticated
endpoint for prometheus, which is required for nagios to
successfully query the prometheus endpoint for its service
checking mechanism
Change-Id: Ia4ccc3c44a89b2c56594be1f4cc28ac07169bf8c
8652e14acb