Bind host security group to staging apps for proxy support
Bind host security group to staging apps for proxy support

* Don't need to pass proxy env vars to garden for docker apps

[Finishes #115691341]

Signed-off-by: Mark DeLillo <cb16bf7df25dbf84b90c1f94696c8a91f946dc1d@pivotal.io>

pivotal-cf/micropcf,pivotal-cf/micropcf