Fix API error object code and display a flash error message

[AparnaKarve]

After #783 merge, the API error object would be in e.error. Related code was adjusted accordingly.

Also failures from the API need to be shown as a flash messages.

[AparnaKarve]

/cc @himdel

[himdel]

Looks good, but I'm wondering if the old e.message still isn't happening somewhere .. any chance this could still be happening in $http requests?

[AparnaKarve]

any chance this could still be happening in $http requests

Not sure, but won't hurt to have both cases in there.
Updated with the change.

(code is slightly repetitious, but I wanted to use minimum number of conditionals)

[miq-bot]

Checked commit AparnaKarve@52fc752 with ruby 2.2.6, rubocop 0.47.1, and haml-lint 0.20.0
0 files checked, 0 offenses detected
Everything looks good. 🏆

[himdel]

@AparnaKarve I was a bit worried that this would make some places flash twice, which is why I didn't do this in #783 ... but looks like you're right, no such place I can see.. works like a charm, thanks! :)

[himdel]

@AparnaKarve just a note, as part of angular2 compatibility effort, I'm going to try making eslint warn about angular.isDefined, and we should stop using it at some point.

I can do a sweep PR so don't worry about it too much, but.. well, angular.isDefined(foo) is just a long way of writing foo !== undefined so.. we can just do that :). (Unless backporting to darga, I'm not sure about IE9 in this regard.)

Just FYI :)