Update the mTotalDuration for each animation in an AnimatorSet.

A cache was introduced in I677bc289f2ba430466f2d90ebc14368cb7b75118 to
optimise calls to createDependencyGraph(), but the update was removed in
If1dc6e8dbc93a4bf5ade8c5b0dcf43d3ee6ba7b5. This patch reintroduces the
update when calculating child animation start/end times to re-enable the
optimisation.

Test: cts-tradefed run cts-dev --module CtsAnimationTestCases
Change-Id: Ie9dad4049c07a151889b57809bf844ab854ff482