Allow empty strings for raw and default types.

Empty string is a perfectly valid raw string and the default type is
meant to prevent malicious characters, not empty strings.

Change-Id: I717bbcfe1a81b383782122870d0d727b28f40cce

os_config_applier/tests/test_value_type.py

@@ -35,3 +35,11 @@ class ValueTypeTestCase(testtools.TestCase):
     def test_default_bad(self):
         self.assertRaises(config_exception.ConfigException,
                           value_types.ensure_type, "foo\nbar", "default")
+
+    def test_default_empty(self):
+        self.assertEqual('',
+                         value_types.ensure_type('', 'default'))
+
+    def test_raw_empty(self):
+        self.assertEqual('',
+                         value_types.ensure_type('', 'raw'))

os_config_applier/value_types.py

@@ -19,8 +19,8 @@ from config_exception import ConfigException
 
 TYPES = {
     "int": "^[0-9]+$",
-    "default": "^[A-Za-z0-9]+$",
-    "raw": "."
+    "default": "^[A-Za-z0-9]*$",
+    "raw": ""
 }