Increase cltv_final

During a meeting earlier this week we agreed with Eclair to temporarily
increase the final CLTV delta in our invoices to establish
compatibility with the already deployed Eclair wallets. They in turn
agreed to remove the enforcement of higher final CLTV deltas, or bump
it locally should it not match their expectations as allowed by
BOLT 11. This has since been implemented in ACINQ/eclair#627.

lightningd/options.c

@@ -500,7 +500,7 @@ static const struct config testnet_config = {
 
 	/* Be aggressive on testnet. */
 	.cltv_expiry_delta = 6,
-	.cltv_final = 6,
+	.cltv_final = 10,
 
 	/* Send commit 10msec after receiving; almost immediately. */
 	.commit_time_ms = 10,
@@ -556,7 +556,7 @@ static const struct config mainnet_config = {
 	 *
 	 * The minimum `cltv_expiry` we will accept for terminal payments: the
 	 * worst case for the terminal node C lower at `2R+G+S` blocks */
-	.cltv_final = 8,
+	.cltv_final = 10,
 
 	/* Send commit 10msec after receiving; almost immediately. */
 	.commit_time_ms = 10,