fs: lockd: Use ktime_get_ns()

Replace the ever recurring:
        ts = ktime_get_ts();
        ns = timespec_to_ns(&ts);
with
        ns = ktime_get_ns();

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Trond Myklebust <trond.myklebust@primarydata.com>
Cc: "J. Bruce Fields" <bfields@fieldses.org>
Signed-off-by: John Stultz <john.stultz@linaro.org>