zerovm-cli/jenkins.sh: grab/publish coverage.xml

coverage.xml is expected to be published by the latest job configuration
in Jenkins. This change copies it out of the test environment container
so that it can be published.
zerovm-cli/build.sh: remove superfluous tox args
Merge pull request #21 from larsbutler/zerovm-cli-test-fixes

zerovm-cli test fixes