Fixed invocation of tools init callbacks

[jrmadsen]

• Fixes scenario where Kokkos::Tools::Experimental::set_init_callback is configured before Kokkos::initialize(...) and there is no library loaded from environment, e.g.:

extern "C"
void init_library(const int loadSeq, const uint64_t interfaceVer,
                  const uint32_t devInfoCount, void* deviceInfo) {
    // ...
}

int main()
{
    Kokkos::Tools::Experimental::set_init_callback(&init_library);
    Kokkos::initialize();
    // ...
    Kokkos::finalize();
}

Will also apply to:

• Experimental::current_callbacks.request_tool_settings
• Experimental::current_callbacks.provide_tool_programming_interface

when the @DavidPoliakoff remembers to create set callback functions for those features ;)

[DavidPoliakoff]

I've literally just been running into this. Good stuff

[crtrott]

@DavidPoliakoff can you (or someone else) add a test for this?