[Review] Request from 'wstephenson' @ 'SUSE/connect/review_140721_handle_zypper_nonzero_returns'

Please review the following changes:
  * a7835cf Revert recipe to test master
  * 239dd15 Move zypper test back to correct place
  * 5f9d527 Remove pending zypper unit test
  * 7b48795 Increase coverage
  * 270474b Remove cmd from error logging; logged previously
  * 6919cc6 Move zypper specific error handling into the zypper case, and report composite error
  * 9f0910e Another attempt to lock git reliably
  * e112cb8 See if the previous successful registration prevents zypper from failing as expected
  * c2e7817 Capture zypper output and report on error
  * 2f0a2d2 Don't put the cucumber process to sleep
  * 2f20e06 Make zypp locking clean
  * 58d5da7 Log zypper errors and exit with zypper return code
  * ce9c279 Include exit status in zypper error
  * 8c42640 typo
  * 1a54ba7 test added in wrong place
  * 31404f5 Merge branch 'master' into review_140721_handle_zypper_nonzero_returns
  * 5ade0ae Merge branch 'master' into review_140721_handle_zypper_nonzero_returns
  * 4afc01d wrong lockfile path
  * ff13351 Use this branch for testing
  * 2c7ecf8 Move hooks to env and test to integration
  * 3b9689f First stab at locking/unlocking libzypp in tests
  * 28d7f6b Merge branch 'master' into review_140721_handle_zypper_nonzero_returns
  * 077a648 Test for locked zypper

``diff
+ # NOTE: zypper with formatter option will return output instead of error
+ # e.g. command 'zypper --xmlout --non-interactive products -i' failed
+ error = error.empty? ? output : error
```

move back to top since it will raise an exception in else condition