Fix for Chromedriver not connecting to adb running on non-default port. Take 2

Fixes #3717 
Depends on appium/appium-adb#47 being merged in.
@jlipps in my first comment I'm explaining why this.adb is needed (`this.adb is needed to restart adb (line 210)`)

it was a preexisting bug which I fixed as a part of the pull request - `this.adb` wasn't defined so when chromedriver couldn't connect to adb it tried to restart it but the variable wasn't there (stumbled upon it while inestigating adb port issue).
It's kind of unrelated to the main fix, but I thought since I'm in this file I would kill two birds with one stone. Didn't anticipate for it to be such an issue :)