Removed stack trace when catches anonymizing data error

[chloe-zh]

Issue #, if available:
#1004 #431

Description of changes:
Removed the stack trace for query data anonymizing error since it causes confusion for users who execute metadata queries and dml queries. Now it only prints a warning in log with error message "Caught an exception when anonymizing sensitive data" as follows:

Giving query show tables like '%'

[2021-01-27T14:31:29,304][WARN ][c.a.o.s.l.u.QueryDataAnonymizer] [147dda5ddf8a.ant.amazon.com] Caught an exception when anonymizing sensitive data
[2021-01-27T14:31:29,305][INFO ][c.a.o.s.l.p.RestSqlAction] [147dda5ddf8a.ant.amazon.com] [a8a76a90-8b90-449e-b50c-44cd954ee851] Incoming request /_opendistro/_sql?pretty=true: 
  show tables like '%'

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov]

Codecov Report

Merging #1014 (7b4562e) into develop (5c19cca) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             develop    #1014   +/-   ##
==========================================
  Coverage      99.87%   99.87%           
  Complexity      2406     2406           
==========================================
  Files            234      234           
  Lines           5526     5526           
  Branches         357      357           
==========================================
  Hits            5519     5519           
  Misses             5        5           
  Partials           2        2           

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[dai-chen]

Thanks for the fix!