Wait for ping succeed before trying SSH in create|get_timestamp methods

Change-Id: Ieece88f5e8cfa80fe6d12720602066dffa5f8d9a
Related-Prod: PRODX-14386
diff --git a/tempest/scenario/manager.py b/tempest/scenario/manager.py
index efdfe8e..1d06f3b 100644
--- a/tempest/scenario/manager.py
+++ b/tempest/scenario/manager.py
@@ -751,6 +751,9 @@
         ssh_client = self.get_remote_client(ip_address,
                                             private_key=private_key,
                                             server=server)
+
+        self.check_vm_connectivity(ip_address, should_connect=True)
+
         if dev_name is not None:
             ssh_client.make_fs(dev_name)
             ssh_client.exec_command('sudo mount /dev/%s %s' % (dev_name,
@@ -768,6 +771,9 @@
         ssh_client = self.get_remote_client(ip_address,
                                             private_key=private_key,
                                             server=server)
+
+        self.check_vm_connectivity(ip_address, should_connect=True)
+
         if dev_name is not None:
             ssh_client.mount(dev_name, mount_path)
         timestamp = ssh_client.exec_command('sudo cat %s/timestamp'