VTU write: Adjust patch_threshold semantic #417

Job	Run time
Automake Serial Minimal Build on Linux	1m 37s
Automake Serial With Clawpack Build on Linux	16m 51s
Automake Serial With GeoClaw Build on Linux	1m 44s
Automake Serial With CudaClaw (CUDA 10.1) Build on Linux	2m 59s
Automake Serial With CudaClaw (CUDA 11.3) Build on Linux	3m 13s
Automake MPI Minimal Build on Linux	2m 16s
Automake MPI Debug With CXX Build on Linux	5m 17s
Automake MPI With Clawpack Build on Linux	17m 0s
Automake MPI With GeoClaw Build on Linux	2m 21s
Automake MPI With CudaClaw (CUDA 10.1) Build on Linux	3m 59s
Automake MPI With CudaClaw (CUDA 11.3) Build on Linux	3m 33s
Automake MPI With ThunderEgg Build on Linux	5m 40s
	1h 6m 30s

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