need to set the default value for LowercaseMetricNames

to fix a name undefined error in kairosdb_writer, or else the writer
would not write outputs to kairosdb due to initialization failure.

Change-Id: Id5756f7caf644616b6da3e3396984bcb52d64a80
Merge "need to set the default value for LowercaseMetricNames" into dev/experimental