No class def found error

[atshaw43]

Issue #, if available:

Description of changes: If a module is needed to serialize an object in Jackson, but it does not exist, then it causes a NoClassDefFoundError

This change will log that error and log which modules are loaded.

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

[codecov-commenter]

Codecov Report

Merging #375 (91825f1) into master (683898a) will increase coverage by 0.00%. The diff coverage is 71.42%.

@@            Coverage Diff            @@
##             master     #375   +/-   ##
=========================================
  Coverage     58.26%   58.27%           
- Complexity     1272     1273    +1     
=========================================
  Files           138      138           
  Lines          5247     5253    +6     
  Branches        633      634    +1     
=========================================
+ Hits           3057     3061    +4     
- Misses         1894     1896    +2     
  Partials        296      296           

Impacted Files	Coverage Δ
...n/java/com/amazonaws/xray/entities/EntityImpl.java	83.77% <71.42%> (-0.47%)	:arrow_down:

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