dialects/mysql-client.js will open and close connection for each query

[spencerdcarlson]

I ran all of the regression tests in test/test-mysql.

[spencerdcarlson]

When closing the db connection, I followed Java's try-with-resources design approach of capturing suppressed errors. https://docs.oracle.com/javase/tutorial/essential/exceptions/tryResourceClose.html#suppressed-exceptions