This commit cuts us over to using placement microversion 1.34 for GET
/allocation_candidates, thereby supporting string request group suffixes
(added in 1.33) when specified in flavor extra_specs.
The mappings (added in 1.34) are not used in code yet, but a future
patch will tie the group suffixes to the RequestGroup.requester_id so
that it can be correlated after GET /a_c. This will allow us to get rid
of map_requested_resources_to_providers, which was a hack to bridge the
gap until we had mappings from placement.
Change-Id: I52499ff6639c1a5815a8557b22dd33106dcc386b
54195a1bd9