Possible bug in using getTagAllocator() in GriddingAlgorithm.C when enabling CUDA

When compiling with CUDA, RAJA and umpire, in my environment with gcc-7, CUDA 10, I noticed that the usage of `getTagAllocator()` in `GriddingAlgorithm.C` to initialize `CellVariables` will cause CUDA illegal memory access when filling those tag variables with `GriddingAlgorithm::fillTags()`. This causes the test sets failure as I mentioned in a previous issue. https://github.com/LLNL/SAMRAI/issues/175

The issue is caused by initialing tag data with tagAllocator, but filling it as a shared memory variable. Replacing `getTagAllocator()` with `getDefaultAllocator()` will temporary resolve this issue and pass all the tests, but I am not sure if this will bring some potential problems.

Start in GriddingAlgorithm.C by tracing how getTagAllocator() initializes CellVariables and how GriddingAlgorithm::fillTags() writes the tag data. Compare this with the proposed getDefaultAllocator() workaround and the test sets referenced through issue #175. Done means the CUDA configuration no longer reports illegal memory access and the affected tests pass without introducing allocator problems.

Written by the indexing model from the issue text.