Various fixes to delete packet and request a little better.
Various fixes to delete packet and request a little better.

src/cpu/simple/timing.cc:
    Various updates for deleting requests more properly.

    The major change is moving the deletion of the fetch request/packet to after the instruction has executed and completed.  This should fix a few bugs because Ron's memory system didn't expect a call for a functional access while a timing access was being processed.

haowu4682/gem5,LingxiaoJIA/gem5,andrewfu0325/gem5-aladdin,andrewfu0325/gem5-aladdin,LingxiaoJIA/gem5,haowu4682/gem5,haowu4682/gem5,haowu4682/gem5,LingxiaoJIA/gem5,andrewfu0325/gem5-aladdin,haowu4682/gem5,haowu4682/gem5,andrewfu0325/gem5-aladdin,LingxiaoJIA/gem5,andrewfu0325/gem5-aladdin,haowu4682/gem5,haowu4682/gem5,LingxiaoJIA/gem5,andrewfu0325/gem5-aladdin,haowu4682/gem5,andrewfu0325/gem5-aladdin,LingxiaoJIA/gem5,LingxiaoJIA/gem5