HPX doesn't shutdown properly

[sithhell]

When calling hpx::init multiple times in an application, the second call to hpx::init fails.
This defect is demonstrated by test/regressions/multiple_init.cpp

[sithhell]

This is especially critical for Android applications. Android keeps the process to reuse the process image. This means that whenever you restart the application, you have to do it twice (the first restart exits ungracefully, if you start the application everything works as expected as the process has been removed due to the crash)