gnocchi have archive policy rule feature, which can control metric's
archive_policy. gnocchi also have a default archive policy rule which
is using low archive policy.

On the other hand, archive_policy is marked as deprecated and will be
removed in the feature in ceilometer[0].

So should better remove archive_policy ceilometer.conf.

[0] https://review.openstack.org/#/c/448586/

Change-Id: I0aa726f6420d628bda3fb4c4eba86b55fe1e2699
Closes-Bug: #1696038