influxDBOut().tag() eats away first letter 't' or 's' from a tag name

First `.tag()` method for influxDBOut() node removes first letter 't' from a tag name (it's weird, I know!)

Example code:
data = stream |
|from()
.measurement('example')
|influxDBOut()
.database('output')
.measurement('result')
.create()
.tag('test_tag', 'foobar')

Expected result:

Tag 'test_tag' in `result`.

Actual result: Tag 'est_tag' in `result`

kapacitor version: 1.5.1-1

Upd: same bug is with starting 's' for fields. f.e. state_duration become a 'tate_duration'.

Reproduce the issue with the provided influxDBOut() pipeline and inspect the implementation behind the .tag() entry point. Verify that tag names beginning with 't' and field names beginning with 's' retain their first characters, then confirm the expected names are written to the result measurement.

Written by the indexing model from the issue text.