Remove create_timestamp & get_timestamp methods

As tempest.scenario.manager was announced stable interface in Tempest 27.0.0[1] it can be now reused in plugins.

Replaced methods:
	* create_timestamp
	* get_timestamp

Etherpad concerning this effort:
https://etherpad.opendev.org/p/tempest-scenario-manager-cleanup

[1] https://docs.openstack.org/releasenotes/tempest/v27.0.0.html#release-notes-27-0-0

Change-Id: Id6ba585c58c0e9b6564d85137fd00ae2a8954c06
diff --git a/barbican_tempest_plugin/tests/scenario/manager.py b/barbican_tempest_plugin/tests/scenario/manager.py
index 275aa3d..4fd005c 100644
--- a/barbican_tempest_plugin/tests/scenario/manager.py
+++ b/barbican_tempest_plugin/tests/scenario/manager.py
@@ -223,36 +223,6 @@
         volume = self.volumes_client.show_volume(volume['id'])['volume']
         self.assertEqual('available', volume['status'])
 
-    def create_timestamp(self, ip_address, dev_name=None, mount_path='/mnt',
-                         private_key=None, server=None):
-        ssh_client = self.get_remote_client(ip_address,
-                                            private_key=private_key,
-                                            server=server)
-        if dev_name is not None:
-            ssh_client.make_fs(dev_name)
-            ssh_client.exec_command('sudo mount /dev/%s %s' % (dev_name,
-                                                               mount_path))
-        cmd_timestamp = 'sudo sh -c "date > %s/timestamp; sync"' % mount_path
-        ssh_client.exec_command(cmd_timestamp)
-        timestamp = ssh_client.exec_command('sudo cat %s/timestamp'
-                                            % mount_path)
-        if dev_name is not None:
-            ssh_client.exec_command('sudo umount %s' % mount_path)
-        return timestamp
-
-    def get_timestamp(self, ip_address, dev_name=None, mount_path='/mnt',
-                      private_key=None, server=None):
-        ssh_client = self.get_remote_client(ip_address,
-                                            private_key=private_key,
-                                            server=server)
-        if dev_name is not None:
-            ssh_client.mount(dev_name, mount_path)
-        timestamp = ssh_client.exec_command('sudo cat %s/timestamp'
-                                            % mount_path)
-        if dev_name is not None:
-            ssh_client.exec_command('sudo umount %s' % mount_path)
-        return timestamp
-
     def get_server_ip(self, server):
         """Get the server fixed or floating IP.