test: set umask explicitly

Some tests which create files and check file permissions assume the
umask is compatible with 022, and break when set to something like 007.
Explicitly set umask to 022

PR-URL: https://github.com/nodejs/node/pull/25213


Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>