Don't send timestamps in UTC

Logstash by itself takes care of conversion of timestamps to UTC, with how it was logstash was showing wrong time for the events.
Revert "Don't send timestamps in UTC"

This reverts commit 4628065f2c823d213d32fcc9f650701f5ea81759.
Send timezone with timestamp, fixes salt #9140
Merge pull request #9140 from viq/patch-3

Send TZ in timestamps to logstash