Fixes subtle bug in zio_handle_io_delay()

Fixed bug introduced in commit #c35b1882. Hinted by gcc:

zio_inject.c: In function ‘zio_handle_io_delay’:
zio_inject.c:382:3: warning: this ‘if’ clause does not guard... [-Wmisleading-indentation]

   if (handler->zi_record.zi_freq != 0 &&
      ^~
      zio_inject.c:384:4: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the ‘if’
          continue;
	      ^~~~~~~~

Signed-off-by: Marcel Huber <marcelhuberfoo@gmail.com>
Signed-off-by: Chunwei Chen <tuxoko@gmail.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #4632