Really Disable RTS before opening port

Signed-off-by: Chris Fiege <chris@tinyhost.de>

sa868/__init__.py

@@ -12,9 +12,13 @@ class SA868(object):
         pass
 
     def __init__(self, port):
-        self._serial = serial.Serial(port, 9200, timeout=1)
-        self._serial.RTS = False
         self._logger = logging.getLogger("SA868")
+        self._serial = serial.Serial()
+        self._serial.rts = False
+        self._serial.port = port
+        self._serial.baudrate = 9600
+        self._serial.timeout = 1
+        self._serial.open()
 
     def _check_freq_range(self, freq):
         if (freq >= 400 and freq <= 480) or (freq >= 134 and freq <=174):