tdb2: make TDB1 code use tdb2's TDB_ERROR and tdb_logerr()

tdb2: make TDB1 code use tdb2's TDB_ERROR and tdb_logerr()

To do this, we make sure that the first few fields of tdb1_context and
tdb_context are the same.

This sweep also fixes up a few paths where we weren't setting
tdb->ecode before our old logging function.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
(Imported from CCAN commit 919937354a331bb964564a11b5a5b80403ff8db9)