gettransaction: fix tests.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
ccan: update (non-blocking I/O working)

This was reported by Nelson Castillo on IRC; dumbwallet was hanging.
He tracked it to this around the same time I saw similar things; pettycoin
would block on large writes (which it does during the sync phase).

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>