aoe: remove call to request handler from I/O completion

There is no need to call the request handler function in the I/O
completion routine.  The user impact of not doing it is a more "nice" aoe
driver that is less susceptible to causing soft lockups.

Signed-off-by: Ed Cashin <ecashin@coraid.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>