improved error handling: esx_advanced_options
* rescue block coverage was too broad
    * transport errors not reported (username, password, etc)
    * rescue clause now 'rescues' only InvalidName
* error message in rescue referenced variable optkey were not in scope
* now reports all keys not found, not just the first one
Merge pull request #152 from rbbrown/improve-esx_advanced_options

improved error handling: esx_advanced_options