At present, all time series are accumulated in the same database in
InfluxDB. This makes queries slow for tenants that have less data. This
patch enables the option to use separate database per tenancy.
This changeset implements the changes on monasca-api which handles read
requests to InfluxDB database.
It also updates the relevant docs providing link to the migration tool
which enables users to migrate their existing data to a database per
tenant model.
Change-Id: I7de6e0faf069b889d3953583b29a876c3d82c62c
Story: 2006331
Task: 36073
967b918bae