blktrace: abort if device ioctl setup fails

blktrace: abort if device ioctl setup fails

If we fail doing the BLKTRACESETUP ioctl, blktrace still marches on
and sets up the rest. This results in errors like the below:

blktrace /dev/sdf
BLKTRACESETUP(2) /dev/sdf failed: 5/Input/output error
Thread 1 failed open /sys/kernel/debug/block/(null)/trace1: 2/No such file or directory
Thread 3 failed open /sys/kernel/debug/block/(null)/trace3: 2/No such file or directory
Thread 2 failed open /sys/kernel/debug/block/(null)/trace2: 2/No such file or directory
[...]
FAILED to start thread on CPU 0: 1/Operation not permitted
FAILED to start thread on CPU 1: 1/Operation not permitted
FAILED to start thread on CPU 2: 1/Operation not permitted

and blktrace continues to run, though it can't do anything in this
state.

If the ioctl setup fails, just abort.

Signed-off-by: Jens Axboe <axboe@kernel.dk>