Don't run opensm on compute nodes

[jabl]

With lots of hosts, opensm can require a non-trivial amount of CPU time. So it shouldn't be run on a compute node where it can disturb batch jobs. Also, with lots of hosts, if all of them run opensm in standby mode I guess there will be a lot of polling on the network to check whether the master is still up.

[martbhell]

OK sounds reasonable :)

However, I think it would be better to keep managing the opensm service but set the service to disabled instead. I'll close this PR and add it manually.

Something like this:

rdma_opensm_enabled: "no"

The task:

- name: Manage the opensm service
  service:
    name: "{{ rdma_opensm_service }}"
    state: "{{ rdma_opensm_state }}"
    enabled: "{{ rdma_opensm_enabled }}"

[jabl]

Thanks, I guess that works too. :)