Modify incorrect import path

SSHExecCommandFailed and TimeoutException are in tempest.lib.

Change-Id: I222b4d0195c49da28a1aacb36c946980f942bd94
diff --git a/tempest/scenario/test_server_basic_ops.py b/tempest/scenario/test_server_basic_ops.py
index 3aab2b8..2d2f7df 100644
--- a/tempest/scenario/test_server_basic_ops.py
+++ b/tempest/scenario/test_server_basic_ops.py
@@ -18,8 +18,8 @@
 
 from tempest.common import waiters
 from tempest import config
-from tempest import exceptions
 from tempest.lib.common.utils import test_utils
+from tempest.lib import exceptions
 from tempest.scenario import manager
 from tempest import test