Fix 4993068: Don't check password history when dpm sets the password

This fixes a crash caused by permission problems when we try to update
the password history and discover there's no password salt.  The code
attempts to create the salt, which triggers the exception.

This could be fixed by wrapping the call with a clearCallingIdentity()/
restoreCallingIdentity(ident).  However, while looking at it, it occurred to me
that this can cause unexpected failures if the DPM tries to set the
password twice or happens to set it to something in the password history.

Instead, we should *always* allow the DPM to reset the password to whatever it wants,
provided it passes the minimum password criteria.

Change-Id: I1505b24f9c097ee5c2c44e4bf378ba90095b113b