fix(autocomplete): clean up md-scroll-mask element on destroy

[cah-alexsukhodolsky]

• added test

Fixes #7049
Fixes #7128

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[cah-alexsukhodolsky]

I signed it!

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CLAs look good, thanks!

[ilovett]

Yep, I ran into this issue on 1.0.5 -- http://codepen.io/anon/pen/ZWWqrM

Seems to be working on 1.0.6 -- http://codepen.io/anon/pen/RaaeMa

[Prozi]

does it work with ngRouter and latest master - I don't think so :/