config+test: increase default num confs for funding flows to 3

In this commit, we increase the default number of confirmations we
require for funding flows from 1 to 3. The value of 1 was rather
unstable on testnet due to the frequent multi-block re-orgs.
Additionally, a value of 3 ensures our funding transaction is
sufficiently buried before we deem is usable.

config.go

@@ -38,7 +38,7 @@ const (
 	defaultPeerPort           = 9735
 	defaultRPCHost            = "localhost"
 	defaultMaxPendingChannels = 1
-	defaultNumChanConfs       = 1
+	defaultNumChanConfs       = 3
 	defaultNoEncryptWallet    = false
 	defaultTrickleDelay       = 30 * 1000
 )