Fix indentation error chrony.conf dhcpv6-relay.yaml

The CloudConfig write_files entry fro chrony.conf is
a nested list, instead of an entry. The file does not
get written.

Change-Id: I5ff6b81c6aaf454fad93e7c2fe2ff5ac68b91261

templates/dhcpv6-relay.yaml

@@ -221,7 +221,7 @@ resources:
               net.ipv6.conf.eth2.forwarding = 1
               net.ipv6.conf.eth3.forwarding = 1
               net.ipv6.conf.all.forwarding = 1
-          - - path: /etc/chrony.conf
+          - path: /etc/chrony.conf
             content:
               str_replace:
                 template: |