Fix bad classname

During refactor https://review.openstack.org/52562 the rename of
BaseComputeAdminTest did not happen at
tempest.api.compute.admin.test_host_negative. This patch corrects the
error.

Fixes bug 1244917

Change-Id: Ia6949b512ee878d9f122117a42a1ac73667bde6b
diff --git a/tempest/api/compute/admin/test_hosts_negative.py b/tempest/api/compute/admin/test_hosts_negative.py
index 9d4c62b..6b24e72 100644
--- a/tempest/api/compute/admin/test_hosts_negative.py
+++ b/tempest/api/compute/admin/test_hosts_negative.py
@@ -20,7 +20,7 @@
 from tempest.test import attr
 
 
-class HostsAdminNegativeTestJSON(base.BaseComputeAdminTest):
+class HostsAdminNegativeTestJSON(base.BaseV2ComputeAdminTest):
 
     """
     Tests hosts API using admin privileges.