CI tests: SELinux setup common for all the tests
    
    Userspace probing needs custom SELinux setup so that systemtap
    can do userspace probing using dyninst.  See check_dyninst_sebools()
    in stapdyn/dynutil.cxx for details.
    
    This update moves such SELinux setup out from the userspace-probes
    testcase, and makes it common for all the systemtap CI tests.