Use fixPacket function everywhere.

Use fixPacket function everywhere.
Fix fixPacket assert function.
Stop timing port from forwarding the request if a response was found in its queue on a read.

src/cpu/memtest/memtest.cc:
src/cpu/memtest/memtest.hh:
src/python/m5/objects/MemTest.py:
    Add parameter to configure what percentage of mem accesses are functional
src/mem/cache/base_cache.cc:
src/mem/cache/cache_impl.hh:
    Use fix Packet function
src/mem/packet.cc:
    Fix an assert that was checking the wrong thing
src/mem/tport.cc:
    Properly detect if we need to do the access to the functional device

--HG--
extra : convert_revision : 447cc1a9a65ddd2a41e937fb09dc0e7c74e9c75e