Fix the build on travis ci by using Log4j2 versions less than 3.0.0-SNAPSHOT.

[PascalSchumacher]

[codecov[bot]]

Codecov Report

Merging #1903 (d566d9c) into dev (ed2da5f) will decrease coverage by 0.41%. The diff coverage is n/a.

@@             Coverage Diff              @@
##                dev    #1903      +/-   ##
============================================
- Coverage     70.75%   70.33%   -0.42%     
+ Complexity      575      572       -3     
============================================
  Files            26       26              
  Lines          2171     2171              
  Branches        311      311              
============================================
- Hits           1536     1527       -9     
- Misses          484      494      +10     
+ Partials        151      150       -1     

Impacted Files	Coverage Δ
...in/java/com/zaxxer/hikari/pool/ProxyStatement.java	46.15% <0.00%> (-3.08%)	:arrow_down:
src/main/java/com/zaxxer/hikari/pool/PoolBase.java	69.96% <0.00%> (-2.20%)	:arrow_down:
...ain/java/com/zaxxer/hikari/util/ConcurrentBag.java	74.46% <0.00%> (-1.07%)	:arrow_down:

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