testing: test CrushWrapper::get_full_location_ordered()
A recent backport of changes to get_full_location_ordered() passed all the make check and RADOS suite tests, but caused failures in the CephFS suite. This turned out to be because the function is barely tested in those suites. Client::get_osd_crush_location() wraps get_full_location_ordered() and covers several more test cases. In particular, it tests:
invalid OSD IDs (which get_full_location_ordered accepts as buckets)
TestCrushWrapper merely checks that after inserting an OSD, get_full_location_ordered() correctly supplies its containing buckets.