fix: Test flake in TestWorkspaceStatus (#4333)

This also changes the status to be on the workspace build, since
that's where the true value is calculated. This exposed a bug where
jobs could never enter the canceled state unless fetched by a
provisioner daemon, which was nice to fix!

See: https://github.com/coder/coder/actions/runs/3175304200/jobs/5173479506

coderd/database/databasefake/databasefake.go

@@ -2238,6 +2238,7 @@ func (q *fakeQuerier) UpdateProvisionerJobWithCancelByID(_ context.Context, arg
 			continue
 		}
 		job.CanceledAt = arg.CanceledAt
+		job.CompletedAt = arg.CompletedAt
 		q.provisionerJobs[index] = job
 		return nil
 	}