s3:lib: fix/simplify srprs_hex()
There're a few problems with this function.
- it pretends to support values up to UINT64_MAX
in it only returns 'unsigned' which support only
values up to UINT32_MAX. Currently we only have
callers with len=2 and len=8, so it's not a triggered
bug.
We just allow (len >= 1 && len <= 8) now.
- The compiler is not able to inspect the format string
to sscanf().
We copy up to 8 bytes into a stack buffer
and always pass "%8x" to sscanf.
Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>