Fix python binary name in arch/SConscript.

Fix python binary name in arch/SConscript.
Also delete no-longer-needed SPARC test.py files (should
have gone with my last chnageset where LiveProcess
became ISA-independent).

src/arch/SConscript:
    Mistakenly committed hard-coded python binary name.
    Should use same python to run isa_parser that was
    used to run scons.

--HG--
extra : convert_revision : a3acd5496f3b930d57bb59ae164b8a4a8065bbf8