tests: reduce number of nodes to run tests

[adammoody]

Some tests in SCR and the components currently require multiple compute nodes. While these do need multiple processes, many of these could be modified to run with multiple processes on a single compute node. That should be done so as to reduce the number of resources needed to run the tests.

A common requirement from some tests is to use the hostname to split procs into groups or to define directories. That would need to be modified to perhaps use process ranks instead.

[adammoody]

• reduce number of nodes for tests to 1 node ECP-VeloC/rankstr#15
• reduce number of nodes for tests to 1 node ECP-VeloC/spath#21
• reduce number of nodes for tests to 1 node ECP-VeloC/KVTree#61
• reduce number of nodes for tests to 1 node ECP-VeloC/AXL#121
• reduce number of nodes for tests to 1 node ECP-VeloC/shuffile#24
• reduce number of nodes for tests to 1 node ECP-VeloC/redset#41
• reduce number of nodes for tests to 1 node ECP-VeloC/er#28

[adammoody]

@kosinovsky , I've created separate issues for each component. It actually looks like we may be able to change all of them. We can use the issue on the component page to discuss details about each component in turn if needed.

These tests do typically require multiple processes, like 2 or 3. Our goal is to change things so that the test can run with all of its processes on a single node. So we want to avoid commands like srun -N3 -n3 and use srun -n3 where we allocate one node instead. Similarly, we want to change from jsrun -r 1 to something like jsrun -r 3 again where we allocate one node.

The redset and er tests will be more involved, as those will require some changes to the test code itself to avoid using hostname.