Revert "Cygwin: passwd/group: allow specifying "." as local computername"

This reverts commit 7c34811440.

This potentially allows to circumvent OpenSSHs user/group name matching,
unless the Admin knows to add every local user twice or to use patterns,
e.g.:

  Match user MACHINE+user,.+user
  Match user *+user

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

winsup/cygwin/uinfo.cc

@@ -2008,14 +2008,6 @@ pwdgrp::fetch_account_from_windows (fetch_user_arg_t &arg, cyg_ldap *pldap)
       if ((p = wcschr (name, cygheap->pg.nss_separator ()[0])))
 	{
 	  fq_name = true;
-	  /* Convenience: Translate domain name "." to local machine. */
-	  if (p == name + 1 && name[0] == L'.')
-	    {
-	      p = wcpcpy (name, cygheap->dom.account_flat_name ());
-	      *p = L'\\';
-	      sys_mbstowcs (p + 1, UNLEN + 1, arg.name + 2);
-	    }
-	  else
 	  *p = L'\\';
 	}
       sid = csid;