This test runs dummy function with coroutine by using
two enter and one yield since which is a common usage.

So we can see the cost introduced by corouting for running
one function, for example:

	Run operation 20000000 iterations 4.841071 s, 4131K operations/s
	242ns per coroutine
Signed-off-by: NMing Lei <ming.lei@canonical.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>