[asan] Fix interception unittest on Windows64.

mov edi,edi is _not_ NOP in 64-bit, use 66,90h instead.
This bug was causing interception unittest to crash on 
Windows64 (windows 8 and windows 10).

Credits to etienneb for finding the root cause.

Patch by: Wei Wang
Differential Revision: http://reviews.llvm.org/D22274

llvm-svn: 275207