Python crash on deleting shared_ptrs stored in a C++ vector

Hi,

There is a struct A defined in C++ and exposed to python as shared_ptr.
There are two global vectors of shared_ptrs of A.
Create and add a object of type A from python to C++ in the two vectors
Clear one vector
Then when the python exits the program crashes with access violation
error, while deleting the shared_ptrs

[TestShared.zip](https://github.com/boostorg/python/files/241747/TestShared.zip)

Environment: Boost 1.58.0, compiler VS 2012

I have attached both C++ and python file to recreate this issue.

Thanks