Fix ASan CHECK failure when exceptions are thrown during early initialization, particularly in Python bindings that load Ceph shared libraries.

ASan reported the following error:

  AddressSanitizer: CHECK failed: asan_interceptors.cpp:335
  "((__interception::real___cxa_throw)) != (0)" (0x0, 0x0)
    #0 CheckUnwind asan_rtl.cpp:69
    #1 CheckFailed sanitizer_termination.cpp:86
    #2 __interceptor___cxa_throw asan_interceptors.cpp:335
    #3 boost::throw_exception<boost::bad_lexical_cast>
    #4 boost::conversion::detail::throw_bad_cast
    #5 boost::lexical_cast<unsigned long, std::string>
    #6 librbd::rbd_features_from_string /ceph/src/librbd/Features.cc:67
    #7 get_rbd_options()::$_2::operator() rbd_options.cc:44
    #8 Option::pre_validate /ceph/src/common/options.cc:94
    #9 md_config_t::md_config_t /ceph/src/common/config.cc:208
    #10 CephContext::CephContext /ceph/src/common/ceph_context.cc:730
    #11 rados_create_cct /ceph/src/librados/librados_c.cc:120
    #12 Python rados module initialization

Root cause: When Python loads the Ceph shared library (e.g., rados.so), CephContext initialization validates configuration options. The RBD default features option validator calls rbd_features_from_string(), which uses boost::lexical_cast to parse the feature string. When the string is not numeric (e.g., "layering,exclusive-lock,..."), lexical_cast throws boost::bad_lexical_cast.

This exception is properly caught and handled in the code. However, ASan's exception interceptor (__cxa_throw) may not be fully initialized when exceptions are thrown during early library initialization, causing a CHECK failure.

Why qa/asan.supp is not sufficient:
The existing suppression in qa/asan.supp for __interceptor___cxa_throw only suppresses ASan reports about the interceptor. It does NOT prevent CHECK failures in ASan's runtime itself. CHECK failures are assertions that terminate the program immediately, before any suppression mechanism can be applied. The CHECK fails because real___cxa_throw is NULL (not yet initialized), which is a precondition violation in ASan's interceptor code.

Suppressions work by filtering ASan's output after an issue is detected, but they cannot prevent internal CHECK failures in ASan's initialization logic.

Solution: Disable ASan's C++ exception interception by adding intercept_cxx_exceptions=0 to ASAN_OPTIONS. This prevents ASan from intercepting exception throws/catches, avoiding the initialization order issue. Exception handling still works correctly; we just lose ASan's ability to detect exception-related memory issues.

This is a known limitation when using ASan with code that throws exceptions during static/early initialization, particularly in shared libraries loaded by interpreters like Python.

Note: This does not hide real bugs - the exception is properly caught and handled. We're only disabling ASan's interception mechanism to avoid the initialization order problem.

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