Fix functest "test_server_metadata()" in test_sever.py

There is only a functional test for "server set" command
in test_server_metadata(), we also need a functional test
for "server unset" command, so I add it in this patch.

Change-Id: I23c40ac1c5adcc2563d8aa9dcb5551df695e98e3

Author: Huanxuan Ao

functional/tests/compute/v2/test_server.py

@@ -129,6 +129,8 @@ def test_server_metadata(self):
         1) Boot server in setUp
         2) Set properties for server
         3) Check server properties in server show output
+        4) Unset properties for server
+        5) Check server properties in server show output
         """
         self.wait_for_status("ACTIVE")
         # metadata
@@ -138,6 +140,12 @@ def test_server_metadata(self):
         raw_output = self.openstack('server show ' + self.NAME + opts)
         self.assertEqual(self.NAME + "\na='b', c='d'\n", raw_output)
 
+        raw_output = self.openstack(
+            'server unset --property a ' + self.NAME)
+        opts = self.get_show_opts(["name", "properties"])
+        raw_output = self.openstack('server show ' + self.NAME + opts)
+        self.assertEqual(self.NAME + "\nc='d'\n", raw_output)
+
     def test_server_suspend_resume(self):
         """Test server suspend and resume commands.