Do not default global option defaults to None

If a global option does not have a default value defined,
we should not set the default value to None, because it
prevents the users of the config object from supplying
their own fallback values.

tuned/utils/global_config.py

@@ -20,8 +20,8 @@ def __init__(self,config_file = consts.GLOBAL_CONFIG_FILE):
 	def get_global_config_spec():
 		"""
 		Easy validation mimicking configobj
-		Returns two dicts, first with default values (default None)
-		global_default[consts.CFG_SOMETHING] = consts.CFG_DEF_SOMETHING or None
+		Returns two dicts, first with default values (if there is one)
+		global_default[consts.CFG_SOMETHING] = consts.CFG_DEF_SOMETHING
 		second with configobj function for value type (default "get" for string, others eg getboolean, getint)
 		global_function[consts.CFG_SOMETHING] = consts.CFG_FUNC_SOMETHING or get
 		}
@@ -30,7 +30,7 @@ def get_global_config_spec():
 				   if opt.startswith("CFG_") and
 				   not opt.startswith("CFG_FUNC_") and
 				   not opt.startswith("CFG_DEF_")]
-		global_default = dict((getattr(consts, opt), getattr(consts, "CFG_DEF_" + opt[4:], None)) for opt in options)
+		global_default = dict((getattr(consts, opt), getattr(consts, "CFG_DEF_" + opt[4:])) for opt in options if hasattr(consts, "CFG_DEF_" + opt[4:]))
 		global_function = dict((getattr(consts, opt), getattr(consts, "CFG_FUNC_" + opt[4:], "get")) for opt in options)
 		return global_default, global_function