New asset-path default causing problems on Node

https://github.com/anmonteiro/lumo had problems with Boot-cljs 2.1

```
❯ boot test
Compiling ClojureScript...
• lumo_test/test_suite.js

;; ======================================================================
;; Testing with Node:

module.js:487
throw err;
^

Error: Cannot find module '/home/juho/.boot/cache/tmp/home/juho/Source/lumo/a6t/3lgroc/lumo_test/lumo_test/test_suite.out/goog/bootstrap/nodejs.js'
```

Previously the default asset-path happened to be correct, due to bug in Boot-cljs: https://github.com/boot-clj/boot-cljs/pull/156
Also related: https://github.com/boot-clj/boot-cljs/commit/3cd71952e55a9d5717a5f190409ee50d3c2d6051

Manually setting `:asset-path` on boot-cljs-test fixes this. There might be bug at boot-cljs-test code: https://github.com/crisptrutski/boot-cljs-test/blob/master/src/crisptrutski/boot_cljs_test/utils.clj#L101 But there could be something wrong with boot-cljs test also as this broke between 2.0 and 2.1.

Reproduce the failure with `boot test` in the linked lumo project using Boot-cljs 2.1. Start by inspecting `boot-cljs-test/src/crisptrutski/boot_cljs_test/utils.clj` around line 101, then compare the referenced Boot-cljs PR and commit. Done means the Node test runs without manually setting `:asset-path`.

Written by the indexing model from the issue text.