Remove database if wallet.Loader.CreateNewWallet errors. (btcsuite#419)

This prevents future calls to CreateNewWallet from erroring due to the
database file existing.

Fixes btcsuite#418.

rpc/documentation/api.md

@@ -1,6 +1,6 @@
 # RPC API Specification
 
-Version: 4.0.1
+Version: 4.0.2
 
 **Note:** This document assumes the reader is familiar with gRPC concepts.
 Refer to the [gRPC Concepts documentation](http://www.grpc.io/docs/guides/concepts.html)

rpc/rpcserver/server.go

@@ -45,10 +45,10 @@ import (
 
 // Public API version constants
 const (
-	semverString = "4.0.1"
+	semverString = "4.0.2"
 	semverMajor  = 4
 	semverMinor  = 0
-	semverPatch  = 1
+	semverPatch  = 2
 )
 
 // translateError creates a new gRPC error with an appropiate error code for

wallet/loader.go

@@ -121,7 +121,7 @@ func (l *Loader) RunAfterLoad(fn func(*Wallet)) {
 // CreateNewWallet creates a new wallet using the provided public and private
 // passphrases.  The seed is optional.  If non-nil, addresses are derived from
 // this seed.  If nil, a secure random seed is generated.
-func (l *Loader) CreateNewWallet(pubPassphrase, privPassphrase, seed []byte) (*Wallet, error) {
+func (l *Loader) CreateNewWallet(pubPassphrase, privPassphrase, seed []byte) (w *Wallet, err error) {
 	defer l.mu.Unlock()
 	l.mu.Lock()
 
@@ -147,6 +147,12 @@ func (l *Loader) CreateNewWallet(pubPassphrase, privPassphrase, seed []byte) (*W
 	if err != nil {
 		return nil, err
 	}
+	// Attempt to remove database file if this function errors.
+	defer func() {
+		if err != nil {
+			_ = os.Remove(dbPath)
+		}
+	}()
 
 	// Initialize the newly created database for the wallet before opening.
 	err = Create(db, pubPassphrase, privPassphrase, seed, l.chainParams,
@@ -157,7 +163,7 @@ func (l *Loader) CreateNewWallet(pubPassphrase, privPassphrase, seed []byte) (*W
 
 	// Open the newly-created wallet.
 	so := l.stakeOptions
-	w, err := Open(db, pubPassphrase, nil, so.VoteBits, so.VoteBitsExtended,
+	w, err = Open(db, pubPassphrase, nil, so.VoteBits, so.VoteBitsExtended,
 		so.StakeMiningEnabled, so.BalanceToMaintain, so.AddressReuse,
 		so.PruneTickets, so.TicketAddress, so.TicketMaxPrice,
 		so.TicketBuyFreq, so.PoolAddress, so.PoolFees, so.TicketFee,