Ocata -> Pike upgrade: when using extra overcloud services the user needs to switch the environment file from environments/services/ to environments/services-docker/

[Marius Cornea]

When upgrading to Pike and moving to containers we need to manually replace the environment file(in Ocata they are located in environments/services/) which activate the extra feature with its correspondent file in environments/services-docker. This is an error prone operation which can lead to unexpected upgrade results in case switching the environment files gets missed by the user. The transition to containerized services should be as much as possible transparent for the user.

[Bogdan Dobrelya (bogdando)]

IIUC, that's how things work upstream and we can do not much but document that