MFC 327753: Simplify some logic by merging an if test with a subsequent switch.

MFC 327753: Simplify some logic by merging an if test with a subsequent switch.

Specifically, in aio_queue_file() the code was doing this:

   if (opcode == LIO_SYNC) {
       ...
   }

   switch (opcode) {
   ...
   case LIO_SYNC:
       ...
   }

This moves the body of the if statement into the LIO_SYNC case of the
switch statement.

Sponsored by:	Chelsio Communications