[test]调整serial.Serial的初始化参数

原始初始化参数为：
return serial.Serial(join(self.input_dir,scales[0]),
#         baudrate = 9600,
#         bytesize = serial.SEVENBITS,
#         stopbits = serial.STOPBITS_ONE,
#         parity   = serial.PARITY_EVEN,
#         #xonxoff  = serial.XON,
#         timeout  = 0.01,
#         writeTimeout= 0.01)

调整为：
return serial.Serial(join(self.input_dir, scales[0]),
baudrate = 4800,
bytesize = serial.EIGHTBITS,
stopbits = serial.STOPBITS_ONE,
parity   = serial.PARITY_NONE,
timeout  = 0.05,
writeTimeout= 0.05)