FIX: potential duplicate log entry due to race condition

[kkonrad]

There was potentially race condition that could lead to situation in which we could get multiple log entries regarding the same keyword being unknown. Such case was when more than one thread was doing check on containsKey before they went into put.

Simple fix for this is to always add element to the UNKNOWN_KEYWORDS map and than check if it was present. See documentation for put method and what value it returns. Doing this that way shouldn't impact performance.

[codecov-commenter]

Codecov Report

Merging #323 into master will decrease coverage by 0.01%.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##             master     #323      +/-   ##
============================================
- Coverage     70.80%   70.79%   -0.02%     
  Complexity      652      652              
============================================
  Files            75       75              
  Lines          2497     2496       -1     
  Branches        529      529              
============================================
- Hits           1768     1767       -1     
  Misses          525      525              
  Partials        204      204              

Impacted Files	Coverage Δ	Complexity Δ
...main/java/com/networknt/schema/JsonMetaSchema.java	83.33% <100.00%> (-0.12%)	16.00 <0.00> (ø)

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[stevehu]

@kkonrad Thanks a lot for your help.