Wipe the user data out in any case.

When the external storage is not mounted, the android system won't
wipe out the user data (i.e. "/data") if wipeData() is called with
the flag WIPE_EXTERNAL_STORAGE.

We think that the user data should be wiped out in any options and
also wipeData(int) method currently supports also for a external
storage. So we will also change the API reference comment.

If we should care about backward compatibility of this method behavior
with the option WIPE_EXTERNAL_STORAGE, then we would add an another
bitmask something like a ALWAYS_RESET.

Change-Id: Id7bf673c722bacc0480d32e46553b9a348513879