Legacy ebtables-save does not use a policy string of '-' to denote
user-defined chains but instead lists them with a policy of ACCEPT.
In order to use ebtables_restore_parse() for ebtables-save
implementation, make use of builtin table definitions to decide whether
a given chain is a builtin one or not.
Signed-off-by: Phil Sutter <phil@nwl.cc> Signed-off-by: Florian Westphal <fw@strlen.de>