Fix formatin of GPS String.

measurement_main.py

                 time_epoch = subprocess.check_output(CMD_TIME_EPOCH, shell=True).decode(
                     "utf-8"
                 )
-                write_to_file(output_file, "{},{}".format(nmea_str, time_epoch))
+                write_to_file(output_file, "{},{}".format(nmea_str.replace("\n", ""), time_epoch))
     except:
         if not ser.is_open:
             print_message("GPS serial port is closed. Exit monitoring thread.")