epoll: ofp_epoll_wait() does not block indefinitely if timeout is -1
epoll: ofp_epoll_wait() does not block indefinitely if timeout is -1

Signed-off-by: Bogdan Pricope <42ca93281c38a50e44216100dfc014dce41a2ed5@linaro.org>
Reviewed-by: Jere Leppänen <14957520de8d9815e0c353a07fe23c737f0171e9@nokia.com>

OpenFastPath/ofp,OpenFastPath/ofp,OpenFastPath/ofp,TolikH/ofp,OpenFastPath/ofp,TolikH/ofp,TolikH/ofp