3.5.8 - Fix intermittent issue with Firefox and geckodriver

Fix intermittent issue with Firefox and geckodriver

• Fix intermittent Firefox issue
• This resolves #1424

The following intermittent issues should all be handled now:

"geckodriver unexpectedly exited"
"Process unexpectedly closed"
"Failed to read marionette port"
"A connection attempt failed"

(For situations caused intermittently by the Firefox auto-update process that checks to see if an update is available, whether to perform the update, and then perform the update if applicable.)