[statsd] Improved LogEvent::parseBody() performance

It is possible to know upfront how many values LogEvent is going to have
vector can reserve requred amount of elements to avoid __push_back_slow_path

Bug: 212755214
Bug: 297437011
Test: statsd_test
Test: statsd_benchmark
Change-Id: Ia327ce714843809788ef9aea8fbcf9181e26bc5e
2 files changed