Merge pull request #432 from jrperritt/rs-keypair-fix

Rackspace keypair fix
diff --git a/rackspace/compute/v2/servers/requests.go b/rackspace/compute/v2/servers/requests.go
index f9424df..d4472a0 100644
--- a/rackspace/compute/v2/servers/requests.go
+++ b/rackspace/compute/v2/servers/requests.go
@@ -117,7 +117,9 @@
 	// key_name doesn't actually come from the extension (or at least isn't documented there) so
 	// we need to add it manually.
 	serverMap := res["server"].(map[string]interface{})
-	serverMap["key_name"] = opts.KeyPair
+	if opts.KeyPair != "" {
+		serverMap["key_name"] = opts.KeyPair
+	}
 
 	return res, nil
 }