Set correct mode for .ssh/authorized_keys files.

Per bug 1182648 we were not setting the mode and as a result couldn't
log in, defeating the purpose of having a local-config element :).

Change-Id: I4114b9536392f1517eac8f4bbe6f4b60ce1186a1

elements/local-config/install.d/62-ssh-key

@@ -7,4 +7,6 @@ set -e
 if [ -e "/tmp/in_target.d/ssh-authorized-keys" ]; then
   mkdir -p /root/.ssh
   cat /tmp/in_target.d/ssh-authorized-keys >> /root/.ssh/authorized_keys
+  chmod 0700 /root/.ssh
+  chmod 0600 /root/.ssh/authorized_keys
 fi