Fixed Bug in DistributedGridSynchronizer
After Tomas's refactorization in commit:
Test GPUDistributedGridIOTest cannot be compiled (nvcc).
It was fixed by partial revert of refactorization in commit:
https://jlk.fjfi.cvut.cz/gitlab/mmg/tnl-dev/commit/68d3e703452944a5d08d1cb0dc8336eb02e90722
Issue is to find why nvcc has in this Test (only) problem with Tomas's code.