WebdavUtils Don't statically allocate the SimpleDateObject

When accessing this from multiple threads we get inconsistent states of
parsed value leading to the wrong date being returned.

putting some traces in " 04-09 15:44:39.596: I/A(3754): I got date: Sun, 26 May 2013 02:18:43 GMT and am using date parse method 1 Which gives date as 1 Jan 1970 01:00:43
.....

Can be proved by shoving a synchronized block in:
```
Date a = new Date ();
    public static Date parseResponseDate(String date) {
   synchronized(a) {
        Date returnDate = null;
        for (int i = 0; i < DATETIME_FORMATS.length; ++i) {
            try {
                  returnDate = DATETIME_FORMATS[i].parse(date);
                  return returnDate;
            } catch (ParseException e) {
              e.printStackTrace ();
            }
        }
    }
        return null;
    }
```

(Which also stops it from producing incorrect results)