guard rmprocs in tests

Author: IanButterworth

test/distributed_exec.jl

@@ -1906,7 +1906,7 @@ end end
 include("splitrange.jl")
 
 # Clear all workers for timeout tests (issue #45785)
-rmprocs(workers())
+nprocs() > 1 && rmprocs(workers())
 begin
     # First, assert that we get no messages when we close a cooperative worker
     w = only(addprocs(1))
@@ -1927,5 +1927,5 @@ end
 
 # Run topology tests last after removing all workers, since a given
 # cluster at any time only supports a single topology.
-rmprocs(workers())
+nprocs() > 1 && rmprocs(workers())
 include("topology.jl")

test/topology.jl

@@ -134,7 +134,7 @@ for (i, (from,to)) in enumerate(combinations)
 end
 
 # With lazy=false, all connections ought to be setup during `addprocs`
-rmprocs(workers())
+nprocs() > 1 && rmprocs(workers())
 addprocs_with_testenv(8; lazy=false)
 def_count_conn()
 @test sum(asyncmap(p->remotecall_fetch(count_connected_workers,p), workers())) == 64