In TestClusterHealthCollector, test all supported versions by default,
and split the osdmap tests for Nautilus vs. Octopus+. There were a
number of tests that included an osdmap that didn't need it, and the
osdmap was removed from them so that version-specific testing would not
be required.
- `ceph.Conn` interface no longer depends on go-ceph/rados,
now defines its own `PoolStat` structure for our use.
- New separate `rados` package that implements the interface
- Merged `mocks` package into `ceph` to avoid circular import
Joshua Baergen
Kyle
Xavier Villaneau