MINOR: fd: make fd_clr_running() return the previous value instead

MINOR: fd: make fd_clr_running() return the previous value instead

It's an AND so it destroys information and due to this there's a call
place where we have to perform two reads to know the previous value
then to change it. With a fetch-and-and instead, in a single operation
we can know if the bit was previously present, which is more efficient.