Add negative test for live migration

No negative test exists to check for conflict response code when live
migration fails for that reason.  Add new negative test for live
migration of VM in suspended state to trigger conflict response code.

Jenkins job tempest-dsvm-neutron-scenario-multinode-lvm-multibackend
gate uses tempest regex that does not pick up the live migration
negative test file with old file name:

DEVSTACK_GATE_TEMPEST_REGEX=
'(^tempest\.(scenario|api\.compute\.admin\.test_(live_|)migration))'

Rename negative live migration file so that it gets picked up by multi
node gate jenkins job.

Change-Id: I1bb9895d99fbc7feca7335df24f2305e261dbb10
diff --git a/tempest/api/compute/base.py b/tempest/api/compute/base.py
index 429ded5..56a976d 100644
--- a/tempest/api/compute/base.py
+++ b/tempest/api/compute/base.py
@@ -479,3 +479,21 @@
         self.addCleanup(client.wait_for_resource_deletion, flavor['id'])
         self.addCleanup(client.delete_flavor, flavor['id'])
         return flavor
+
+    def get_host_for_server(self, server_id):
+        server_details = self.admin_servers_client.show_server(server_id)
+        return server_details['server']['OS-EXT-SRV-ATTR:host']
+
+    def get_host_other_than(self, server_id):
+        source_host = self.get_host_for_server(server_id)
+
+        list_hosts_resp = self.os_admin.hosts_client.list_hosts()['hosts']
+        hosts = [
+            host_record['host_name']
+            for host_record in list_hosts_resp
+            if host_record['service'] == 'compute'
+        ]
+
+        for target_host in hosts:
+            if source_host != target_host:
+                return target_host