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

Change-Id: Ieece88f5e8cfa80fe6d12720602066dffa5f8d9a
Related-Prod: PRODX-14386
(cherry picked from commit 5e522e625386c39361e5370e11e749071285b5e9)
(cherry picked from commit b5cd7d94276bf6b6785b04c7bbccbe231bb68d2d)
diff --git a/tempest/scenario/manager.py b/tempest/scenario/manager.py
index 39021d5..39d6e38 100644
--- a/tempest/scenario/manager.py
+++ b/tempest/scenario/manager.py
@@ -1066,6 +1066,7 @@
                                             private_key=private_key,
                                             server=server,
                                             username=username)
+        self.check_vm_connectivity(ip_address)
 
         if dev_name is not None:
             ssh_client.make_fs(dev_name, fs=fs)
@@ -1099,6 +1100,8 @@
                                             server=server,
                                             username=username)
 
+        self.check_vm_connectivity(ip_address)
+
         if dev_name is not None:
             ssh_client.mount(dev_name, mount_path)
         timestamp = ssh_client.exec_command('sudo cat %s/timestamp'