mpi: fix multi conditional for allreduce #8312

Job	Run time
pytest-ubuntu-py312-gcc13-omp-base	51m 42s
pytest-ubuntu-py312-gcc12-cxxomp-base	56m 26s
pytest-ubuntu-py310-gcc14-omp-base	44m 53s
pytest-ubuntu-py310-gcc9-omp-base	45m 10s
pytest-ubuntu-py311-gcc10-noomp-base	41m 8s
pytest-ubuntu-py310-gcc14-omp-adjoint	32m 38s
pytest-ubuntu-py311-gcc11-cxxnoomp-adjoint	32m 53s
pytest-osx-py312-clang-omp-base	27m 51s
pytest-ubuntu-py311-gcc11-cxxnoomp-base	45m 30s
pytest-ubuntu-py312-gcc12-cxxomp-adjoint	39m 35s
pytest-ubuntu-py312-gcc13-omp-adjoint	38m 39s
pytest-ubuntu-py311-gcc10-noomp-adjoint	30m 18s
pytest-docker-py310-icx-omp-adjoint	28m 9s
pytest-docker-py310-gcc-omp-base	38m 24s
pytest-docker-py310-gcc-omp-adjoint	28m 3s
pytest-ubuntu-py313-gcc14-omp-adjoint	40m 13s
pytest-ubuntu-py313-gcc14-omp-base	55m 9s
pytest-ubuntu-py310-gcc9-omp-adjoint	33m 2s
pytest-docker-py310-icx-omp-base	32m 10s
	12h 21m 53s

Provide feedback