test: use anonymous volume for prune (#3051)

This is related to moby/moby#44216

Prunes will, by default, no longer prune named volumes, only anonymous ones.

Signed-off-by: Brian Goff <cpuguy83@gmail.com>

tests/integration/api_volume_test.py

@@ -57,11 +57,10 @@ def test_force_remove_volume(self):
 
     @requires_api_version('1.25')
     def test_prune_volumes(self):
-        name = 'hopelessmasquerade'
-        self.client.create_volume(name)
-        self.tmp_volumes.append(name)
+        v = self.client.create_volume()
+        self.tmp_volumes.append(v["Name"])
         result = self.client.prune_volumes()
-        assert name in result['VolumesDeleted']
+        assert v["Name"] in result['VolumesDeleted']
 
     def test_remove_nonexistent_volume(self):
         name = 'shootthebullet'