Write secrets to tmpfs

So that we may avoid writing the decrypted contents of secrets to
disk, write them to a file in a tmpfs.

Change-Id: I7c029b67d0fc2fa3827dc811137dd4f3a90706d8
diff --git a/tests/unit/test_v3.py b/tests/unit/test_v3.py
index 2293ca0..eb11edf 100755
--- a/tests/unit/test_v3.py
+++ b/tests/unit/test_v3.py
@@ -1283,8 +1283,7 @@
         ], ordered=False)
         matches = self.searchForContent(self.history[0].jobdir.root,
                                         b'test-password')
-        self.assertEqual(set(['/ansible/playbook_0/secrets.yaml',
-                              '/work/secret-file.txt']),
+        self.assertEqual(set(['/work/secret-file.txt']),
                          set(matches))
 
     def test_secret_file(self):
@@ -1319,8 +1318,7 @@
         ], ordered=False)
         matches = self.searchForContent(self.history[0].jobdir.root,
                                         b'test-password')
-        self.assertEqual(set(['/ansible/playbook_0/secrets.yaml',
-                              '/work/failure-file.txt']),
+        self.assertEqual(set(['/work/failure-file.txt']),
                          set(matches))
 
     def test_secret_file_fail(self):