Fix curve properties not applying when dismissing task

- ag/10936255 replaced getViewCenterPosition() with getChildStart(),
  meaning getTranslationX() was no longer included.
- This change goes back to using getViewCenterPosition() and renames
  it to getChildStartWithTranslation().
- Update typo with parameter in getCurveProperties being mInsets
  instead of insets.

Bug: 153574162
Change-Id: I9b46daecf3ee6dbefe0270e70fdc5e6d9d0b0c00