profilers.systemtap : fix import error when using systemtap profiler

Now under profiler/systemtap miss the file __init__.py, so when using
systemtap profiler will report import error like:
    "no module named systemtap"
This patch fix this error, and add some systemtap scripts for qemu test

Signed-off-by: Yunping Zheng <yunzheng@redhat.com>