auth/credentials: add cli_credentials_set_utf16_password()

auth/credentials: add cli_credentials_set_utf16_password()

We need a way to initialize the cli_credentials from the raw utf16 blob,
which might not be completely valid utf16, which means the conversion
from CH_UTF16MUNGED to CH_UTF8 might loose information.

This would result in an invalid nt_hash, when we convert back
from CH_UTF8 to CH_UTF16LE.

Bug: https://bugzilla.samba.org/show_bug.cgi?id=11016

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>