avocado.settings: Do a better job returning list values

Use python's ast module to safely evaluate the list values.
Signed-off-by: NLucas Meneghel Rodrigues <lmr@redhat.com>

avocado/core/settings.py

@@ -15,6 +15,7 @@
 """
 Reads the avocado settings from a .ini file (from python ConfigParser).
 """
+import ast
 import ConfigParser
 import os
 import sys
@@ -129,8 +130,7 @@ def convert_value_type(value, value_type):
             return True
 
     if value_type == list:
-        # Split the string using ',' and return a list
-        return [val.strip() for val in sval.split(',')]
+        return ast.literal_eval(sval)
 
     conv_val = value_type(sval)
     return conv_val

selftests/all/unit/avocado/settings_unittest.py

@@ -20,7 +20,7 @@ str_key = frobnicate
 int_key = 1
 float_key = 1.25
 bool_key = True
-list_key = I, love, settings
+list_key = ['I', 'love', 'settings']
 empty_key =
 """