Add support for k8s 1.8.15 (#3464)

Author: Cecile Robert-Michon

pkg/api/common/versions.go

@@ -41,6 +41,7 @@ var AllKubernetesSupportedVersions = map[string]bool{
 	"1.8.12":         true,
 	"1.8.13":         true,
 	"1.8.14":         true,
+	"1.8.15":         true,
 	"1.9.0":          true,
 	"1.9.1":          true,
 	"1.9.2":          true,
@@ -223,6 +224,7 @@ func getAllKubernetesWindowsSupportedVersionsMap() map[string]bool {
 		"1.7.1",
 		"1.8.13",
 		"1.8.14",
+		"1.8.15",
 		"1.10.0-beta.2",
 		"1.10.0-beta.4",
 		"1.10.0-rc.1",