io_u: ensure to invalidate cache on time_based random reads

io_u: ensure to invalidate cache on time_based random reads

We need to do this with the file reset and retrieval of a
new offset, not of it fails.

Fixes: 0bcf41cdc22df ("io_u: re-invalidate cache when looping around without file open/close")
Signed-off-by: Jens Axboe <axboe@kernel.dk>