build: update btcwallet dependency to address SendOutputs bug

In this commit, we update our btcwallet dependency to include the latest
changes that aim to address the recently discovered SendOutputs bug.

This commit will also allow the lnwallet test case added in the
previous commit to succeed.

Gopkg.lock

@@ -106,7 +106,7 @@
   revision = "ab6388e0c60ae4834a1f57511e20c17b5f78be4b"
 
 [[projects]]
-  digest = "1:2995aa2bcb95d13a8df309e1dcb6ac20786acb90df5a090bf5e07c2086219ce8"
+  digest = "1:014bf3112e2bc78db2409f1d7b328c642fe27f2e0b5983595b240bf12578f335"
   name = "github.com/btcsuite/btcwallet"
   packages = [
     "chain",
@@ -127,7 +127,7 @@
     "wtxmgr",
   ]
   pruneopts = "UT"
-  revision = "6d43b2e29b5eef0f000a301ee6fbd146db75d118"
+  revision = "4c01c0878c4ea6ff80711dbfe49e49199ca07607"
 
 [[projects]]
   branch = "master"

Gopkg.toml

@@ -72,7 +72,7 @@
 
 [[constraint]]
   name = "github.com/btcsuite/btcwallet"
-  revision = "6d43b2e29b5eef0f000a301ee6fbd146db75d118"
+  revision = "4c01c0878c4ea6ff80711dbfe49e49199ca07607"
 
 [[constraint]]
   name = "github.com/tv42/zbase32"