(ITS#6338) dnParent(x, x) can remove \0-termination

[h . b . furuseth]

Full_Name: Hallvard B Furuseth
Version: HEAD, RE24
OS: 
URL: 
Submission from: (NULL) (129.240.6.233)
Submitted by: hallvard


This:
    struct berval x = BER_BVC("cn=foo");
    dnParent(x, x);
keeps x.bv_val pointing at "cn=foo" instead of at the \0
behind it.  bv_len is correctly set to 0 though.

Fixing.