s3:utils: Do not overflow the destination buffer in net_idmap_restore()

s3:utils: Do not overflow the destination buffer in net_idmap_restore()

Found by covsan.

error[invalidScanfFormatWidth]: Width 128 given in format string (no. 2)
is larger than destination buffer 'sid_string[128]', use %127s to
prevent overflowing it.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=13567

Pair-Programmed-With: Justin Stephenson <jstephen@redhat.com>
Signed-off-by: Andreas Schneider <asn@samba.org>
Signed-off-by: Justin Stephenson <jstephen@redhat.com>
Reviewed-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>