burst_buffer/cray: accept jobs without dw_wlm_cli

burst_buffer/cray: Accept new jobs on backup slurmctld daemon without access
    to dw_wlm_cli command. No burst buffer actions will take place. Newly
    submitted jobs will be accepted and stay in pending state. Jobs depedent
    upon stage-in or stage-out will remain in their current state until the
    action can take place.