internal/oem: drop noop OEMs

Drop legacy Container Linux OEMs with no code in Ignition: cloudsigma,
exoscale, hyperv, interoute, niftycloud, rackspace*, vagrant.  Leave
pxe because it's typically configured with coreos.config.url.

internal/oem/oem.go

@@ -77,10 +77,6 @@ func init() {
 		name:  "azure",
 		fetch: azure.FetchConfig,
 	})
-	configs.Register(Config{
-		name:  "cloudsigma",
-		fetch: noop.FetchConfig,
-	})
 	configs.Register(Config{
 		name:  "cloudstack",
 		fetch: cloudstack.FetchConfig,
@@ -102,22 +98,10 @@ func init() {
 		fetch:      ec2.FetchConfig,
 		newFetcher: ec2.NewFetcher,
 	})
-	configs.Register(Config{
-		name:  "exoscale",
-		fetch: noop.FetchConfig,
-	})
 	configs.Register(Config{
 		name:  "gce",
 		fetch: gce.FetchConfig,
 	})
-	configs.Register(Config{
-		name:  "hyperv",
-		fetch: noop.FetchConfig,
-	})
-	configs.Register(Config{
-		name:  "niftycloud",
-		fetch: noop.FetchConfig,
-	})
 	configs.Register(Config{
 		name:   "packet",
 		fetch:  packet.FetchConfig,
@@ -127,18 +111,6 @@ func init() {
 		name:  "pxe",
 		fetch: noop.FetchConfig,
 	})
-	configs.Register(Config{
-		name:  "rackspace",
-		fetch: noop.FetchConfig,
-	})
-	configs.Register(Config{
-		name:  "rackspace-onmetal",
-		fetch: noop.FetchConfig,
-	})
-	configs.Register(Config{
-		name:  "vagrant",
-		fetch: noop.FetchConfig,
-	})
 	configs.Register(Config{
 		name:  "vagrant-virtualbox",
 		fetch: virtualbox.FetchConfig,
@@ -151,10 +123,6 @@ func init() {
 		name:  "vmware",
 		fetch: vmware.FetchConfig,
 	})
-	configs.Register(Config{
-		name:  "interoute",
-		fetch: noop.FetchConfig,
-	})
 	configs.Register(Config{
 		name:  "qemu",
 		fetch: qemu.FetchConfig,