Currently the mapping to collect host info of instance is not correct,
and unfortunately, we can only get a hexdigest of project_id + host_name.
But we can get the correct host name by using the same algorithm when
doing billing.
Closes-Bug: #1665191
Change-Id: I0585c1e9a01250e6b34f3c1d060b76db34fcd6bf
b2e57549e9