Bump cirros version to 0.6.3

This is the latest cirros release, featuring an updated kernel and some
fixes and added features, let's use it.

[0] https://github.com/cirros-dev/cirros/releases/tag/0.6.3

Change-Id: I2506fa713e0426789fa40a5f4f7fd4e963a158f0
diff --git a/stackrc b/stackrc
index 0b3e1c6..b9f86d1 100644
--- a/stackrc
+++ b/stackrc
@@ -656,7 +656,7 @@
 
 #IMAGE_URLS="https://download.cirros-cloud.net/${CIRROS_VERSION}/cirros-${CIRROS_VERSION}-${CIRROS_ARCH}-disk.img" # cirros full disk image
 
-CIRROS_VERSION=${CIRROS_VERSION:-"0.6.2"}
+CIRROS_VERSION=${CIRROS_VERSION:-"0.6.3"}
 CIRROS_ARCH=${CIRROS_ARCH:-$(uname -m)}
 
 # Set default image based on ``VIRT_DRIVER`` and ``LIBVIRT_TYPE``, either of
@@ -673,11 +673,11 @@
                 lxc) # the cirros root disk in the uec tarball is empty, so it will not work for lxc
                     DEFAULT_IMAGE_NAME=${DEFAULT_IMAGE_NAME:-cirros-${CIRROS_VERSION}-${CIRROS_ARCH}-rootfs}
                     DEFAULT_IMAGE_FILE_NAME=${DEFAULT_IMAGE_FILE_NAME:-cirros-${CIRROS_VERSION}-${CIRROS_ARCH}-rootfs.img.gz}
-                    IMAGE_URLS+="https://download.cirros-cloud.net/${CIRROS_VERSION}/${DEFAULT_IMAGE_FILE_NAME}";;
+                    IMAGE_URLS+="https://github.com/cirros-dev/cirros/releases/download/${CIRROS_VERSION}/${DEFAULT_IMAGE_FILE_NAME}";;
                 *) # otherwise, use the qcow image
                     DEFAULT_IMAGE_NAME=${DEFAULT_IMAGE_NAME:-cirros-${CIRROS_VERSION}-${CIRROS_ARCH}-disk}
                     DEFAULT_IMAGE_FILE_NAME=${DEFAULT_IMAGE_FILE_NAME:-cirros-${CIRROS_VERSION}-${CIRROS_ARCH}-disk.img}
-                    IMAGE_URLS+="https://download.cirros-cloud.net/${CIRROS_VERSION}/${DEFAULT_IMAGE_FILE_NAME}";;
+                    IMAGE_URLS+="https://github.com/cirros-dev/cirros/releases/download/${CIRROS_VERSION}/${DEFAULT_IMAGE_FILE_NAME}";;
                 esac
             ;;
         vsphere)
@@ -688,7 +688,7 @@
             # Use the same as the default for libvirt
             DEFAULT_IMAGE_NAME=${DEFAULT_IMAGE_NAME:-cirros-${CIRROS_VERSION}-${CIRROS_ARCH}-disk}
             DEFAULT_IMAGE_FILE_NAME=${DEFAULT_IMAGE_FILE_NAME:-cirros-${CIRROS_VERSION}-${CIRROS_ARCH}-disk.img}
-            IMAGE_URLS+="http://download.cirros-cloud.net/${CIRROS_VERSION}/${DEFAULT_IMAGE_FILE_NAME}";;
+            IMAGE_URLS+="https://github.com/cirros-dev/cirros/releases/download/${CIRROS_VERSION}/${DEFAULT_IMAGE_FILE_NAME}";;
     esac
     DOWNLOAD_DEFAULT_IMAGES=False
 fi