tdb2: catch errors in tdb1_needs_recovery()

tdb2: catch errors in tdb1_needs_recovery()

The tdb1 backend simply returns "true" if there's an error determining
if a tdb needs recovery.  But this leads failtest down a rabbit hole;
it's better to return the error at this case (and makes for better for
diagnostics, since they will come from the first fault, not later in
tdb1_transaction_recover().

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
(Imported from CCAN commit 332d0c29baa6896e67c439aeb47f58a104fbc781)