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/queries/provisionerjobs.sql

@@ -78,7 +78,8 @@ WHERE
 UPDATE
 	provisioner_jobs
 SET
-	canceled_at = $2
+	canceled_at = $2,
+	completed_at = $3
 WHERE
 	id = $1;