lib: Modify event system to treat fd access more fairly

lib: Modify event system to treat fd access more fairly

Keep track of the last starting spot of where fd's were
being handled for read operations.  Modify the io read
handler to cycle through the list of fd's that need
to be handled such that fd's at the front do not take
precedence for being handled all the time.

Signed-off-by: Donald Sharp <sharpd@nvidia.com>