test: fixed the execution for the threasfafe function test

PR-URL: https://github.com/nodejs/node-addon-api/pull/807
Fixes: https://github.com/nodejs/node-addon-api/issues/806
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>
-sh-4.2$

• Commit a13b36c
• Compare 9aceea7..a13b36c
• Branch master

NickNaso authored Michael Dawson committed