test images: rebases the kitten and nautilus images

The current kitten and nautilus images are depending on agnhost:2.14, which
has not been built, since the Image Promoter was not working at the time.

Author: claudiubelu

test/images/kitten/BASEIMAGE

@@ -1,8 +1,8 @@
-linux/amd64=REGISTRY/agnhost:2.14-linux-amd64
-linux/arm=REGISTRY/agnhost:2.14-linux-arm
-linux/arm64=REGISTRY/agnhost:2.14-linux-arm64
-linux/ppc64le=REGISTRY/agnhost:2.14-linux-ppc64le
-linux/s390x=REGISTRY/agnhost:2.14-linux-s390x
-windows/amd64/1809=REGISTRY/agnhost:2.14-windows-amd64-1809
-windows/amd64/1903=REGISTRY/agnhost:2.14-windows-amd64-1903
-windows/amd64/1909=REGISTRY/agnhost:2.14-windows-amd64-1909
+linux/amd64=REGISTRY/agnhost:2.19-linux-amd64
+linux/arm=REGISTRY/agnhost:2.19-linux-arm
+linux/arm64=REGISTRY/agnhost:2.19-linux-arm64
+linux/ppc64le=REGISTRY/agnhost:2.19-linux-ppc64le
+linux/s390x=REGISTRY/agnhost:2.19-linux-s390x
+windows/amd64/1809=REGISTRY/agnhost:2.19-windows-amd64-1809
+windows/amd64/1903=REGISTRY/agnhost:2.19-windows-amd64-1903
+windows/amd64/1909=REGISTRY/agnhost:2.19-windows-amd64-1909

test/images/nautilus/BASEIMAGE

@@ -1,8 +1,8 @@
-linux/amd64=REGISTRY/agnhost:2.14-linux-amd64
-linux/arm=REGISTRY/agnhost:2.14-linux-arm
-linux/arm64=REGISTRY/agnhost:2.14-linux-arm64
-linux/ppc64le=REGISTRY/agnhost:2.14-linux-ppc64le
-linux/s390x=REGISTRY/agnhost:2.14-linux-s390x
-windows/amd64/1809=REGISTRY/agnhost:2.14-windows-amd64-1809
-windows/amd64/1903=REGISTRY/agnhost:2.14-windows-amd64-1903
-windows/amd64/1909=REGISTRY/agnhost:2.14-windows-amd64-1909
+linux/amd64=REGISTRY/agnhost:2.19-linux-amd64
+linux/arm=REGISTRY/agnhost:2.19-linux-arm
+linux/arm64=REGISTRY/agnhost:2.19-linux-arm64
+linux/ppc64le=REGISTRY/agnhost:2.19-linux-ppc64le
+linux/s390x=REGISTRY/agnhost:2.19-linux-s390x
+windows/amd64/1809=REGISTRY/agnhost:2.19-windows-amd64-1809
+windows/amd64/1903=REGISTRY/agnhost:2.19-windows-amd64-1903
+windows/amd64/1909=REGISTRY/agnhost:2.19-windows-amd64-1909