Fix key store address hex decoding and accounts test

Thanks to https://github.com/jaekwon for original fix!

crypto/key_store_plain.go

@@ -119,8 +119,11 @@ func GetKeyAddresses(keysDirPath string) (addresses [][]byte, err error) {
 	}
 	addresses = make([][]byte, len(fileInfos))
 	for i, fileInfo := range fileInfos {
-		addresses[i] = make([]byte, 40)
-		addresses[i] = []byte(fileInfo.Name())
+		address, err := hex.DecodeString(fileInfo.Name())
+		if err != nil {
+			continue
+		}
+		addresses[i] = address
 	}
 	return addresses, err
 }