test: set umask for tests

nodejs#25213 proposes setting umask in the
Python test runner to avoid spurious test failures when running from a
shell with a restrictive umask. This is a good idea, but will only fix
the issue for tests run with the Python runner. Set it in
`common/index.js` as well so that it fixes it even when tests are run
directly with a `node` binary, bypassing the Python test runner.

test/common/index.js

@@ -34,6 +34,10 @@ const {
   hasIntl
 } = process.binding('config');
 
+// Some tests assume a umask of 0o022 so set that up front. Tests that need a
+// different umask will set it themselves.
+process.umask(0o022);
+
 const noop = () => {};
 
 const hasCrypto = Boolean(process.versions.openssl);