Fix typo in network_data files

The comments use ipv6_gateway, while the actual data
and code uses gateway_ipv6. This changes the comments
to use gateway_ipv6 as well.

Change-Id: I3b173fca479e778f75307b7bb47bd7954ea786f4

network_data.yaml

@@ -22,7 +22,7 @@
 # ipv6_subnet: Optional, sets default IPv6 subnet if IPv4 is already defined.
 # ipv6_allocation_pools: Set default IPv6 allocation pools if IPv4 allocation pools
 #                        are already defined.
-# ipv6_gateway: Set an IPv6 gateway if IPv4 gateway already defined.
+# gateway_ipv6: Set an IPv6 gateway if IPv4 gateway already defined.
 # ipv6: If ip_subnet not defined, this specifies that the network is IPv6-only.
 # NOTE: IP-related values set parameter defaults in templates, may be overridden,
 # either by operators, or e.g in environments/network-isolation-v6.yaml where we

network_data_ganesha.yaml

@@ -19,7 +19,7 @@
 # ipv6_subnet: Optional, sets default IPv6 subnet if IPv4 is already defined.
 # ipv6_allocation_pools: Set default IPv6 allocation pools if IPv4 allocation pools
 #                        are already defined.
-# ipv6_gateway: Set an IPv6 gateway if IPv4 gateway already defined.
+# gateway_ipv6: Set an IPv6 gateway if IPv4 gateway already defined.
 # ipv6: If ip_subnet not defined, this specifies that the network is IPv6-only.
 # NOTE: IP-related values set parameter defaults in templates, may be overridden,
 # either by operators, or e.g in environments/network-isolation-v6.yaml where we

network_data_routed.yaml

@@ -29,7 +29,7 @@
 # ipv6_subnet: Optional, sets default IPv6 subnet if IPv4 is already defined.
 # ipv6_allocation_pools: Set default IPv6 allocation pools if IPv4 allocation pools
 #                        are already defined.
-# ipv6_gateway: Set an IPv6 gateway if IPv4 gateway already defined.
+# gateway_ipv6: Set an IPv6 gateway if IPv4 gateway already defined.
 # routes_ipv6: Optional, list of networks that should be routed via network gateway.
 #              Example: [{'destination':'fd00:fd00:fd00:3004::/64',
 #                         'nexthop':'fd00:fd00:fd00:3000::1'}]