Sync tenants with tenant service

[hrishin]

Idler retrieves tenants information only once during the boot time. Its doesn't get updated until next restart.
A side effect of such issue is, Idler, keeps stale deployments despite those deployments got de-provisioned.
Hence it results in HTTP 404 when it tries to idle Jenkins deployment. It also needs to remove state builds for associated deployments.

Idler needs to sync with tenant service and remove deleted deployments.

• Provide an API a delete tenant API for tenant service. So tenant service would consume it
  or
• Sync peridocially with tenant-service

[hrishin]

Would help in fixing #315