Backdrop bug when using multiple modals and appendTo

[letmejustfixthat]

When multiple modals are created (at the same time) only a single backdrop will be created. My use case: Let's say we have a list of items, designed business cardish. I want to be able to delete those from my view by clicking a link. Than a confirmation modal appears with the backdrop only above that specific card. When opening a seconds modal dialog, while the first one is stil active no second backdrop will be created. Only the z-index will be updated.

https://run.plnkr.co/plunks/nwGf2MfgeQ51zom3w9aR/#

There should always be a new backdrop created, when a new modal instance is created, shouldn't it?

Versions:
Angular: 1.4.8
UIBS: 2.1.3
Bootstrap: 3.3.5

[wesleycho]

This is tightly related to #2678.