Bug 1090853 - Move cancelMMI to dialer app terminated, ...

prevent canceling any MMI session started by operator
We should be already handling this case here:

https://github.com/mozilla-b2g/gaia/blob/ce8144588fa701b6ee96bf3120110d135c40e036/apps/communications/dialer/js/mmi_ui.js#L98

I think that the added code here is unnecessary.