topology: Two off-by-one error when catching up with the blockchain

There are two very hard problems in software engineering:

 1. Off-by-one errors

In this case we were rolling back further than needed and we were starting the
catchup one block further than expected.

Signed-off-by: Christian Decker <decker.christian@gmail.com>

lightningd/chaintopology.c

@@ -573,7 +573,7 @@ static void get_init_blockhash(struct bitcoind *bitcoind, u32 blockcount,
 
 	/* Rollback to the given blockheight, so we start track
 	 * correctly again */
-	wallet_blocks_rollback(topo->wallet, topo->first_blocknum - 1);
+	wallet_blocks_rollback(topo->wallet, topo->first_blocknum);
 
 	/* Get up to speed with topology. */
 	bitcoind_getblockhash(bitcoind, topo->first_blocknum,

wallet/wallet.c

@@ -2027,7 +2027,7 @@ void wallet_block_remove(struct wallet *w, struct block *b)
 void wallet_blocks_rollback(struct wallet *w, u32 height)
 {
 	sqlite3_stmt *stmt = db_prepare(w->db, "DELETE FROM blocks "
-					"WHERE height >= ?");
+					"WHERE height > ?");
 	sqlite3_bind_int(stmt, 1, height);
 	db_exec_prepared(w->db, stmt);
 }