ioengines: have ioengines with commit do own io accounting for trims

ioengines: have ioengines with commit do own io accounting for trims

ioengines.c:td_io_queue has a special case where it calls
io_u_mark_submit() and io_u_mark_complete() when the io_u
is a trim operation or when the ioengine does not have a
commit function. This patch makes these two calls the
responsibility of the ioengine for trim io_u's when the
ioengine does have a commit function.

This only applies to libaio because it is the only ioengine
supporting trims with a commit function. All other ioengines that
support trim operations do not have a commit function. These
ioengines are: falloc, glusterfs_async, mmap, mtd, posixaio,
rados, rbd, splice, sync, psync, pvsync, pvsync2.