Bugfix for #360

[gabrielcarioca]

We were using a deprecated perform method without the env parameter coming from it, meaning we were not getting environment variables sent to the build from Jenkinsfile, for example.

Updated the perform and generateReport methods to inherit and use the proper environment variables set by the user.

Resolves #360

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Testing done

I've tested it local and in our company pipeline that were failing as we couldn't set the JAVA_HOME for the allure command to run.

Before: Even though JAVA_HOME was properly set, as we can see from the logs, the execution failed

After: Properly found the JAVA_HOME sent as a parameter and created the allure report

For a pipeline we had running in linux in which we sent the jdk parameter it continued working as before.

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