Material button lollipop shape fix

[vicmns]

[Android Lollipop][Buttons] Fallback when updating drawable shapes. (closes #1797)

Changing a button shape in Lollipop doesn't affect the view ripple drawable, which overflows the background drawable:

This change introduces a fallback only for Lollipop, in which we recreate the background drawable when the shape changes (As it is currently done when changing the drawable insets):

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[vicmns]

@googlebot I signed it!

[drchen]

IS_LOLLIPOP_OR_ABOVE?

[vicmns]

Good point, wasn't "IS_MIN" and old used convention in Android when gating min API logic? I'm pretty sure that I saw some time ago code using this prefix.

[drchen]

I guess Android uses atLeastXXXX in many places, which also works. : )