Switch to cached selenium package

[Alexander Kislitsky]

Our UI tests download selenium package for every test run. And sometimes fail because of networking issues.

We need a possibility to provide selenium package as a file om the filesystem, so that we can cache the file or install as a system package.

[13:45:23] Using gulpfile ~/workspace/verify-fuel-web-ui/nailgun/gulpfile.js
[13:45:23] Starting 'functional-tests'...
[13:45:23] Starting 'selenium:fetch'...
[13:45:28] 'selenium:fetch' errored after 5.11 s
[13:45:28] Error: Could not request headers from http://selenium-release.storage.googleapis.com/2.45/selenium-server-standalone-2.45.0.jar: Error: connect ENETUNREACH
    at Request.<anonymous> (/home/jenkins/workspace/verify-fuel-web-ui_VENV/node_modules/selenium-standalone/lib/install.js:285:8)
    at Request.g (events.js:180:16)
    at Request.EventEmitter.emit (events.js:95:17)
    at Request.onRequestError (/home/jenkins/workspace/verify-fuel-web-ui_VENV/node_modules/selenium-standalone/node_modules/request/request.js:971:8)
    at ClientRequest.EventEmitter.emit (events.js:95:17)
    at Socket.socketErrorListener (http.js:1547:9)
    at Socket.EventEmitter.emit (events.js:95:17)
    at net.js:441:14
    at process._tickCallback (node.js:415:13)

[Igor Belikov (ibelikov)]

Alexander, it was 1 failure caused by external resource unavailability (http://selenium-release.storage.googleapis.com/2.45/selenium-server-standalone-2.45.0.jar) or network problems. Just ask for a retrigger next time

[Aleksandra Fedorova (bookwar)]

I 've changed bug description. We need to be able to use pre-downloaded selenium package

[Vitaly Kramskikh (vkramskikh)]

Skimmed through the code - it doesn't redownload selenium/drivers every time, it just looks for ETag header to check if the current version is valid. Will try to submit a PR to disable this behaviour.