Improve arg-parsing for Selenium Grid usage
This change improves how the command-line args are used to construct the server address for connecting to a Selenium Grid. If the port is included in the --server arg, then that will be used instead of adding on the port via --port. Additionally, if the port is specified separately with --port (as it was previously), then the port will now get added to the correct location in the server address string if the server URL included multiple slashes.
(See https://seleniumbase.io/seleniumbase/utilities/selenium_grid/ReadMe/ for the complete Selenium Grid usage instructions.)