Test endpoint using the set SQL_LOGIN_TIMEOUT value

With this change when the entered endpoint is unreachable Tableau will
warn the user during connection setup instead of proceeding with an
incorrect endpoint and failing during query time. The timeout value set
by Tableau is used when testing the endpoint.
Per the coding conventions, we prefer camel case to underscores (except in file names, where the D convention is to be all lowercase to gracefully handle file system differences).