config: deprecate - in favor of _ for key names

In all of the YAML tags, - has been replaced with _. normalizeConfig() and
normalizeKeys() have also been added to perform the normalization of the input
cloud-config.

As part of the normalization process, falsey values are converted to "false".
The "off" update strategy is no exception and as a result the "off" update
strategy has been changed to "false".

system/update.go

@@ -126,7 +126,7 @@ func (uc Update) Units() []Unit {
 			Runtime: true,
 		}}
 
-		if uc.Update.RebootStrategy == "off" {
+		if uc.Update.RebootStrategy == "false" {
 			ls.Command = "stop"
 			ls.Mask = true
 		}

system/update_test.go

@@ -73,7 +73,7 @@ func TestUpdateUnits(t *testing.T) {
 			}}},
 		},
 		{
-			config: config.Update{RebootStrategy: "off"},
+			config: config.Update{RebootStrategy: "false"},
 			units: []Unit{{config.Unit{
 				Name:    "locksmithd.service",
 				Command: "stop",
@@ -101,7 +101,7 @@ func TestUpdateFile(t *testing.T) {
 		},
 		{
 			config: config.Update{RebootStrategy: "wizzlewazzle"},
-			err:    errors.New("invalid value \"wizzlewazzle\" for option \"RebootStrategy\" (valid options: \"best-effort,etcd-lock,reboot,off\")"),
+			err:    errors.New("invalid value \"wizzlewazzle\" for option \"RebootStrategy\" (valid options: \"best-effort,etcd-lock,reboot,false\")"),
 		},
 		{
 			config: config.Update{Group: "master", Server: "http://foo.com"},
@@ -136,9 +136,9 @@ func TestUpdateFile(t *testing.T) {
 			}},
 		},
 		{
-			config: config.Update{RebootStrategy: "off"},
+			config: config.Update{RebootStrategy: "false"},
 			file: &File{config.File{
-				Content:            "REBOOT_STRATEGY=off\n",
+				Content:            "REBOOT_STRATEGY=false\n",
 				Path:               "etc/coreos/update.conf",
 				RawFilePermissions: "0644",
 			}},