spec: set remote_url for safari(saucelabs)
spec: set remote_url for safari(saucelabs)

https://gerrit.instructure.com/#/c/93921/7/spec/selenium/test_setup/selenium_driver_setup.rb
changed selenium_url to return chrome or firefox remote url

test plan
- start sauce connect locally
- set following selenium_configs
  remote_url: "http://INST_Canvas:bcfbcf36-35cb-4cf0-b0b8-7a80d71c12d1@ondemand.saucelabs.com:80/wd/hub"
  tunnel_id: "canvas_chrome_from_local"
  platform: "Windows 10"
  browser: "safari"
  version: "8.0"
  platform: "OS X 10.10"
- verify that spec run on saucelabs using safari browser
- verify that docker chrome and firefox works

Change-Id: Iecd166d91685c2ae29bf260cd59f6f206c65c41c
Reviewed-on: https://gerrit.instructure.com/96663
Tested-by: Jenkins
Reviewed-by: Cemal Aktas <92f142e4a145271fd784e7ddaa1fc1ff0aed3773@instructure.com>
Reviewed-by: Landon Wilkins <e219b0c23c4256074cdfc7a23138e4f17200b08f@instructure.com>
Product-Review: Santosh Natarajan <513d2c120bea51d9a73bf68ff9748cbc4aba4443@instructure.com>
QA-Review: Santosh Natarajan <513d2c120bea51d9a73bf68ff9748cbc4aba4443@instructure.com>

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