Statsd: support atom counts of new atoms.

In Q, mainline modules will can add atoms after the platform ships.
Statsdstats now supports atom counts of up to 100 atoms that are added
after Q ships. Note: pixel/oem pushed atoms will also get counted now.

Also fixes a typo in prepareFirstBucket

Bug: 131448746
Bug: 128363379
Test: statsd_test
Change-Id: I149c91136fb7649f0c9a0d6e83bc20f8461e45e2