[DEV-279] Make sure fifo is non-blocking

My mistake. I had read that using O_WRONLY or O_RDONLY will make the
fifo blocking, but I had assumed if one side was set to O_RDWR then it
wouldn't matter. Using O_RDWR in all cases should fix the issue.
Don't clear the request list from the request table when the desired request is at the front
Add helpful time function
Clarify pop_request()