Adding --keep-alive option to prevent deletion/creation of vms when running errand

[#81966000]

Signed-off-by: Stev Witzel <switzel@pivotal.io>
Integration Tests for errands keep-alive option

[#81966000]
Set keep_alive to false by default

[#81966000]

Signed-off-by: Tyler Schultz <tschultz@pivotal.io>