This makes it match the function name much more closely.
While we are in here, also fix a bug where the multi-threaded
version would not quit immediately after the future completes.
And also add tests for both of these situations.

Signed-off-by: Chris Lalancette <clalancette@gmail.com>

Signed-off-by: Chris Lalancette <clalancette@gmail.com>

Because we are executing the handler directly, we don't
need to store it and check for futures later.  We can just
check the result immediately.

Signed-off-by: Chris Lalancette <clalancette@gmail.com>