kvdb web tests fail

[marlonhanks]

as expected, in headless envs without chrome/firefox, kvdb web tests will fail:

Set timeout to 20 seconds...
Running headless tests in Firefox on `http://127.0.0.1:39961/`
Try find `webdriver.json` for configure browser's capabilities:
Not found
driver status: signal: 9
driver stdout:
    1615406106300       geckodriver     INFO    Listening on 127.0.0.1:39961

Error: non-200 response code: 500
{"value":{"error":"session not created","message":"Expected browser binary location, but unable to find binary in default location, no 'moz:firefoxOptions.binary' capability provided, and no binary flag set on the command line","stacktrace":""}}
error: test failed, to rerun pass '--test indexed_db'