Fix statsd dropping metrics data.

We can increase the buffer of metrics we store in statsd memory, but
we still request the clients to call getData when the metrics memory
exceeds 128 KB (previously was 90% of 128 KB).

Bug: 76171061
Test: Test that unit-tests still pass.
Change-Id: I901545b364ed313af8c033ce9b40d3cfadb93213