Rename duplicated class name AttachVolumeMultiAttachTest

Class name AttachVolumeMultiAttachTest is duplicated in
api.compute.admin.test_volume_swap.py and
api.compute.volumes.test_attach_volume.py, which is not
good for code readability, so this is to rename
test_volume_swap.AttachVolumeMultiAttachTest
to a more suitable name "TestMultiAttachVolumeSwap".

Change-Id: I079d54a6bf05dc4ce3a217236b6f7c42470bc479
diff --git a/tempest/api/compute/admin/test_volume_swap.py b/tempest/api/compute/admin/test_volume_swap.py
index 99bad8f..ed8cf20 100644
--- a/tempest/api/compute/admin/test_volume_swap.py
+++ b/tempest/api/compute/admin/test_volume_swap.py
@@ -126,13 +126,13 @@
         self.assertIn(volume1['id'], vol_attachments[0]['volumeId'])
 
 
-class AttachVolumeMultiAttachTest(TestVolumeSwapBase):
+class TestMultiAttachVolumeSwap(TestVolumeSwapBase):
     min_microversion = '2.60'
     max_microversion = 'latest'
 
     @classmethod
     def skip_checks(cls):
-        super(AttachVolumeMultiAttachTest, cls).skip_checks()
+        super(TestMultiAttachVolumeSwap, cls).skip_checks()
         if not CONF.compute_feature_enabled.volume_multiattach:
             raise cls.skipException('Volume multi-attach is not available.')