Avoid using nprocs keyword in dask-ssh if set to one
It's complex and gets in the way.  It also assumes that the underlying
dask-worker command supports it (which may not be universally true as we allow
more dask-worker commands).
Concretely my motivation for this is for dask-cuda-worker
@@ -219,7 +219,8 @@ def start_worker(logdir, scheduler_addr, scheduler_port, worker_addr, nthreads,
cmd = ('{python} -m {remote_dask_worker} '
'{scheduler_addr}:{scheduler_port} '
- '--nthreads {nthreads} --nprocs {nprocs} ')
+ '--nthreads {nthreads}'
+ + ('--nprocs {nprocs}' if nprocs != 1 else ''))
if not nohost:
cmd += ' --host {worker_addr} '
