Parametrize target_dir for the timestamp

The default location where we write timestamp files is
/tmp, however, this location does not work for all systems -
/tmp directory cannot be expected to persist across reboots
of an instance.

This commit allows users to set their preferred location and
override the default (/tmp) target dir.

Closes-Bug: #2051268
Change-Id: Id23ae70001525c8eb95d6baf0aca2b4d399e63a1

releasenotes/notes/Add-scenario-config-opt-target-dir-5a969b64be1dc718.yaml

@@ -0,0 +1,7 @@
+---
+features:
+  - |
+    Adding a new config options `[scenario]/target_dir` which allows
+    users to specify the location where timestamps files will be
+    written to. The default value is /tmp that, however, cannot be
+    expected to persist across reboots of an instance.

tempest/config.py

@@ -1217,7 +1217,10 @@ ScenarioGroup = [
                default='icmp',
                choices=('icmp', 'tcp', 'udp'),
                help='The protocol used in security groups tests to check '
-                    'connectivity.')
+                    'connectivity.'),
+    cfg.StrOpt('target_dir',
+               default='/tmp',
+               help='Directory in which to write the timestamp file.'),
 ]
 
 

tempest/scenario/manager.py

@@ -1227,7 +1227,7 @@ class ScenarioTest(tempest.test.BaseTestCase):
         # Default the directory in which to write the timestamp file to /tmp
         # and only use the mount_path as the target directory if we mounted
         # dev_name to mount_path.
-        target_dir = '/tmp'
+        target_dir = CONF.scenario.target_dir
         if dev_name is not None:
             mount_path = os.path.join(mount_path, dev_name)
             ssh_client.make_fs(dev_name, fs=fs)
@@ -1266,7 +1266,7 @@ class ScenarioTest(tempest.test.BaseTestCase):
         # Default the directory from which to read the timestamp file to /tmp
         # and only use the mount_path as the target directory if we mounted
         # dev_name to mount_path.
-        target_dir = '/tmp'
+        target_dir = CONF.scenario.target_dir
         if dev_name is not None:
             mount_path = os.path.join(mount_path, dev_name)
             ssh_client.mkdir(mount_path)