CVE-2019-3880 s3: rpc: winreg: Remove implementations of SaveKey/RestoreKey.

CVE-2019-3880 s3: rpc: winreg: Remove implementations of SaveKey/RestoreKey.

The were not using VFS backend calls and could only work
locally, and were unsafe against symlink races and other
security issues.

If the incoming handle is valid, return WERR_BAD_PATHNAME.

[MS-RRP] states "The format of the file name is implementation-specific"
so ensure we don't allow this.

As reported by Michael Hanselmann.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=13851

Signed-off-by: Jeremy Allison <jra@samba.org>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>