[WIP] fix multigrid agglomeration #8123

Job	Run time
Build SU2 (BaseMPI)	12m 51s
Build SU2 (ReverseMPI)	4m 41s
Build SU2 (ForwardMPI)	4m 24s
Build SU2 (BaseNoMPI)	3m 43s
Build SU2 (asan) (BaseNoMPI-asan)	7m 24s
Build SU2 (ReverseNoMPI)	4m 27s
Build SU2 (tsan) (BaseOMP-tsan)	11m 34s
Build SU2 (asan) (ReverseNoMPI-asan)	10m 18s
Build SU2 (ForwardNoMPI)	4m 13s
Build SU2 (tsan) (ReverseOMP-tsan)	28m 22s
Build SU2 (BaseOMP)	3m 17s
Build SU2 (ReverseOMP)	4m 7s
Build SU2 (ForwardOMP)	3m 28s
Address Sanitizer Tests	0s
Regression Tests	0s
Unit Tests	0s
Thread Sanitizer Tests (hybrid_regression.py)	27m 9s
Thread Sanitizer Tests (hybrid_regression_AD.py)	10m 59s
	2h 20m 57s

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