vacuum: fix crash on vacuum abort
Martin Schwenke discovered that
517f05e42f17766b1e8db8f1f4789cbad968e304
("freeze: abort vacuuming when we're going to freeze.") used ctdb_db for
a logging message which is in fact uninitialized, causing a crash (even
if it wasn't actually logged).
Initialize it properly. Also fix incorrect format in another logging
message introduced in that same change.
CQ:S1019093
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
(cherry picked from commit
8e518950ba281502318d6300f7a5ec6cdf6b5674)