Fix Redis url, an extra "tcp://" was added

[PierreF]

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• CHANGELOG.md updated
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In PR #1480 a extra "tcp://" was added in default configuration. It was due to a OR instead of AND used in if test.

It result in:

$ ./build/telegraf -input-filter redis -output-filter influxdb -sample-config > sample.conf
$ ./build/telegraf -config sample.conf -test
* Plugin: redis, Collection 1
2016/07/19 15:50:06 Errors encountered: [Unable to connect to redis server 'tcp:': dial tcp: lookup tcp on 127.0.1.1:53: no such host]

[sparrc]

thx @PierreF