Extend value for allowed_network_downtime to check server readability more than 5s

Related-Bug: PRODX-39418

Change-Id: I95deaa4ffc24b5675109b1f80ef5fbb48e5d927b
(cherry picked from commit 8b2e0e43204c999a0aae1d7cb3d7855b8fd7dbb4)
(cherry picked from commit b96794968f3a9e473d94bf445a50923489cf0b65)
diff --git a/tempest/config.py b/tempest/config.py
index 2e51eb3..94e0b5d 100644
--- a/tempest/config.py
+++ b/tempest/config.py
@@ -991,7 +991,7 @@
                choices=['ecdsa', 'rsa'],
                help='Type of key to use for ssh connections.'),
     cfg.FloatOpt('allowed_network_downtime',
-                 default=5.0,
+                 default=10.0,
                  help="Allowed VM network connection downtime during live "
                       "migration, in seconds. "
                       "When the measured downtime exceeds this value, an "