Full bucket should be reset even when the last bucket is invalid.

If the bucket is not reset, we will sum the data from the previous
bucket and the next bucket.

As well, the value should only be added to the full bucket if the value
is set.

Bug: 128521677
Test: atest statsd_test
Change-Id: I45bf924a5d2966044cecda34fff84b7cbfe070b0