Previously, any timeout value for which (timeout * hz) will overflow the signed integer, will give weird results, since callout(9) routines will convert negative values of ticks to '1'. For unsigned integer overflow we will get sufficiently smaller timeout values than expected.
Switch from callout_reset, which requires conversion to int based ticks to callout_reset_sbt to avoid this.
This was based on the original work done by Eygene Ryabinkin <rea@freebsd.org> back in 5 Aug 2011 which used a macro to help avoid the overlow.