Fix delay()

Fix delay()

Somewhat amazingly it went unnoticed that the delay() function
doesn't actually cause the task to block.  Since the task state
is never changed from TASK_RUNNING before schedule_timeout() the
scheduler allows to task to continue running without any delay.
Using schedule_timeout_interruptible() resolves the issue by
correctly setting TASK_UNINTERRUPTIBLE.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>