switching off exemplar in queries

[g11tech]

Motivation
We get 404 not found in the grafana queries on some instances for queries which have exemplar feature on for query fetch in dashboard panels.
Switching off the exemplar fetches for these queries, since we don't currently use this feature.

Description

Closes #issue_number

Steps to test or reproduce

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[codeclimate]

Code Climate has analyzed commit 416aae6 and detected 0 issues on this pull request.

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[dapplion]

Looks great! Thanks, please post here once you confirm this fixes the 404 issue

[codecov]

Codecov Report

Merging #3114 (416aae6) into master (6fae286) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #3114   +/-   ##
=======================================
  Coverage   59.06%   59.06%           
=======================================
  Files         377      377           
  Lines        9067     9067           
  Branches     1336     1336           
=======================================
  Hits         5355     5355           
  Misses       3329     3329           
  Partials      383      383           

[g11tech]

Looks great! Thanks, please post here once you confirm this fixes the 404 issue

yes, already tested.