Remove hyphen from rand_name calls in image tests

data_utils.rand_name() appends randam charactors with a hypen like:

 def rand_name(name=''):
     randbits = str(random.randint(1, 0x7fffffff))
     if name:
         return name + '-' + randbits

So it is not necessary to specify a hypen in caller side.
This patch removes a hypen in image tests

Change-Id: Iac422b107ca558e5b41d9ad3fbde051b012df56c
diff --git a/tempest/api/image/v2/test_images.py b/tempest/api/image/v2/test_images.py
index 0997c9f..a00296c 100644
--- a/tempest/api/image/v2/test_images.py
+++ b/tempest/api/image/v2/test_images.py
@@ -150,7 +150,7 @@
         """
         size = random.randint(1024, 4096)
         image_file = StringIO.StringIO(data_utils.random_bytes(size))
-        name = data_utils.rand_name('image-')
+        name = data_utils.rand_name('image')
         body = cls.create_image(name=name,
                                 container_format=container_format,
                                 disk_format=disk_format,
diff --git a/tempest/api/image/v2/test_images_tags.py b/tempest/api/image/v2/test_images_tags.py
index bdb1679..8c71db7 100644
--- a/tempest/api/image/v2/test_images_tags.py
+++ b/tempest/api/image/v2/test_images_tags.py
@@ -27,7 +27,7 @@
                                  disk_format='raw',
                                  visibility='private')
         image_id = body['id']
-        tag = data_utils.rand_name('tag-')
+        tag = data_utils.rand_name('tag')
         self.addCleanup(self.client.delete_image, image_id)
 
         # Creating image tag and verify it.
diff --git a/tempest/api/image/v2/test_images_tags_negative.py b/tempest/api/image/v2/test_images_tags_negative.py
index 13ef27d..227d35f 100644
--- a/tempest/api/image/v2/test_images_tags_negative.py
+++ b/tempest/api/image/v2/test_images_tags_negative.py
@@ -27,7 +27,7 @@
     @test.idempotent_id('8cd30f82-6f9a-4c6e-8034-c1b51fba43d9')
     def test_update_tags_for_non_existing_image(self):
         # Update tag with non existing image.
-        tag = data_utils.rand_name('tag-')
+        tag = data_utils.rand_name('tag')
         non_exist_image = str(uuid.uuid4())
         self.assertRaises(lib_exc.NotFound, self.client.add_image_tag,
                           non_exist_image, tag)
@@ -41,7 +41,7 @@
                                  visibility='private'
                                  )
         image_id = body['id']
-        tag = data_utils.rand_name('non-exist-tag-')
+        tag = data_utils.rand_name('non-exist-tag')
         self.addCleanup(self.client.delete_image, image_id)
         self.assertRaises(lib_exc.NotFound, self.client.delete_image_tag,
                           image_id, tag)