Use Tempest-lib's aggregate client

Aggregate service client has been migrated to tempest-lib-
Ia20fd3914aa6e5ac829bfd3fb88bb4f654958b53

Now Tempest-lib provides this client as stable interface so Tempest
should start using this from lib and remove its own copy.
Also remove other files for this client like response schema, unit tests.

This commits makes Tempest to use aggregate client from Tempest-lib.

Change-Id: I238c688beff26f63e804ebe86101205eb2c0c57c
Depends-on: I516d4119fd200c79a8be4598cbb0d732344e8b75
diff --git a/tempest/clients.py b/tempest/clients.py
index cffdc3f..276f7eb 100644
--- a/tempest/clients.py
+++ b/tempest/clients.py
@@ -17,6 +17,7 @@
 
 from oslo_log import log as logging
 from tempest_lib.services.compute.agents_client import AgentsClient
+from tempest_lib.services.compute.aggregates_client import AggregatesClient
 from tempest_lib.services.identity.v2.token_client import TokenClient
 from tempest_lib.services.identity.v3.token_client import V3TokenClient
 
@@ -28,8 +29,6 @@
 from tempest.services.baremetal.v1.json.baremetal_client import \
     BaremetalClient
 from tempest.services import botoclients
-from tempest.services.compute.json.aggregates_client import \
-    AggregatesClient
 from tempest.services.compute.json.availability_zone_client import \
     AvailabilityZoneClient
 from tempest.services.compute.json.baremetal_nodes_client import \