Only complain when overwriting with a different value

TimeSparseArray only stores one value per timestamp. It complains when a
value is overwritten to ensure that callers do not lose data
unintentionally. However, when a caller may overwrite a value by itself,
it is less risky, even though redundant. Reducing the severity of the
log in this case.

Test: FrameworksCoreTests:TimeSparseArrayTest

Bug: 279599693
Change-Id: If91be39b2c5d7042d0bc6f6afc5313194b8dfbf8