do reset the env values when --reset is used

[hmalphettes]

When I use cf push --reset with a manifest I noticed that the environment variables were not re-applied as defined in the manifest.

This patch does apply the environment variables as defined in the manifest with a cf push --reset.

This PR was originally made against the vmc codebase in cloudfoundry-attic/manifests-vmc-plugin#2
@austinbv suggested I port it to cf.

[dmrschmidt]

Thanks for your pull request! Right now however we cannot merge it in directly without sufficient test coverage. We still have this on our radar and will eventually come to implementing it, however we are currently very busy with other high-priority stories. So if you'd like to contribute and get this fix in we'd really appreciate specs added to the Pull Request and we can merge it in easily.

[hmalphettes]

Ok: I was hoping you would say this :)

[mariash]

Closing for now. Please reopen if you want to add sufficient test coverage.

Thanks,
@mariash & @monkeyherder