lnd_test: define global test timeouts

In preparation for the added propagation delay by separating the miner
and the chain backend, we increase several timeouts throughout the test,
and extract them into constants that can easily be altered.

lnd_test.go

@@ -43,7 +43,12 @@ var (
 )
 
 const (
-	testFeeBase = 1e+6
+	testFeeBase         = 1e+6
+	defaultCSV          = lntest.DefaultCSV
+	defaultTimeout      = lntest.DefaultTimeout
+	minerMempoolTimeout = lntest.MinerMempoolTimeout
+	channelOpenTimeout  = lntest.ChannelOpenTimeout
+	channelCloseTimeout = lntest.ChannelCloseTimeout
 )
 
 // harnessTest wraps a regular testing.T providing enhanced error detection