init-runonce: use CirrOS 0.6.0

CirrOS 0.6.0 was released yesterday. Has newer kernel and userspace,
better network configuration (more IPv6 stuff) and some other
improvements.

Change-Id: Ife7767904efe64602531fa3eb163c78260650909

tools/init-runonce

@@ -19,9 +19,10 @@ fi
 # to be created.
 
 ARCH=$(uname -m)
+CIRROS_RELEASE=0.6.0
 IMAGE_PATH=/opt/cache/files/
-IMAGE_URL=https://github.com/cirros-dev/cirros/releases/download/0.5.1/
-IMAGE=cirros-0.5.1-${ARCH}-disk.img
+IMAGE_URL=https://github.com/cirros-dev/cirros/releases/download/${CIRROS_RELEASE}/
+IMAGE=cirros-${CIRROS_RELEASE}-${ARCH}-disk.img
 IMAGE_NAME=cirros
 IMAGE_TYPE=linux