Shaker reports throughput/ping values as None for the first and last
few seconds of the test for synchronization. Currently we are pushing
null values also to ES, which most likely is affecting averages etc.
This commit prevents shaker from reporting these values to Elasticsearch.
Fixing linting errors in lib/Elastic.py
Change-Id: Ib8aaf425d68fae1254c3692ebf39e885888e497a