Fixes 'Unable to read handler file in function' error for Java runtime

[shazron]

Fixes #138

In the base class base.js function getArtifactZip, we already read the zipfile into a buffer

serverless-openwhisk/compile/functions/runtimes/base.js

Line 83 in 7ffcbef

return this.getArtifactZip(functionObject)

. This is then passed to the subclass' processActionPackage function, in this case in java.js

serverless-openwhisk/compile/functions/runtimes/java.js

Line 36 in 7ffcbef

processActionPackage(handlerFile, zip) {

, which thinks the zip parameter is a JSZip object, thus it all fails with a NPE since zip.file does not evaluate. We just need toreturn zip in the function.

On a cursory review, I think other runtimes may make this mistake as well I think: https://github.com/serverless/serverless-openwhisk/search?q=processActionPackage&unscoped_q=processActionPackage

[codecov-io]

Codecov Report

Merging #139 into master will decrease coverage by 0.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #139      +/-   ##
==========================================
- Coverage   83.56%   83.54%   -0.02%     
==========================================
  Files          46       46              
  Lines        1649     1647       -2     
  Branches      332      332              
==========================================
- Hits         1378     1376       -2     
  Misses        271      271

Impacted Files	Coverage Δ
compile/functions/runtimes/java.js	100% <100%> (ø)	⬆️

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