devel/samurai: Update to latest commit.

While here, re-enable load-based scheduling. It was turned off by
default upstream because, per the commit message disabling it:

Many platforms don't have getloadavg or hide it behind platform-
specific defines. Rather than try to work around it with an ifdef
maze, disable it by default.

FreeBSD's getloadavg works as advertised, and frankly load-based
scheduling is one of the main reasons one might choose samurai over
ninja.