Address pull request comments

* Further simplify "constructor" function's allocation of structs
* Fix formatting

crypto/key_store_passphrase.go

@@ -89,10 +89,7 @@ type keyStorePassphrase struct {
 }
 
 func NewKeyStorePassphrase(path string) KeyStore2 {
-	ks := &keyStorePassphrase{
-		keysDirPath : path,
-	}
-	return ks
+	return &keyStorePassphrase{path}
 }
 
 func (ks keyStorePassphrase) GenerateNewKey(rand io.Reader, auth string) (key *Key, err error) {

crypto/key_store_plain.go

@@ -54,9 +54,7 @@ func DefaultDataDir() string {
 }
 
 func NewKeyStorePlain(path string) KeyStore2 {
-	ks := new(keyStorePlain)
-	ks.keysDirPath = path
-	return ks
+	return &keyStorePlain{path}
 }
 
 func (ks keyStorePlain) GenerateNewKey(rand io.Reader, auth string) (key *Key, err error) {