OPAL_ENABLE_THREAD_MULTI usage on v2.x

[jsquyres]

@hjelmn @bosilca There is a use of OPAL_ENABLE_THREAD_MULTI in bml/r2 on v2.x that is causing a compiler warning (because it isn't defined). This macro is not used in bml/r2 on master. With all the thread changes on master recently, I don't know whether it is safe to just delete this #if or not.

Master:

    /* do it last, for the lazy initialization check in bml_base_get* */
    opal_atomic_wmb();
    proc->proc_endpoints[OMPI_PROC_ENDPOINT_TAG_BML] = bml_endpoint;

v2.x:

    /* do it last, for the lazy initialization check in bml_base_get* */
#if OPAL_ENABLE_THREAD_MULTI
    opal_atomic_wmb();
#endif /* OPAL_ENABLE_THREAD_MULTI */
    proc->proc_endpoints[OMPI_PROC_ENDPOINT_TAG_BML] = bml_endpoint;

Please investigate.

[hjelmn]

Just delete it. It hasn't existed for a long time.

[jsquyres]

Closed via open-mpi/ompi-release#1236