Provide a command to freeze and thaw a service

[Kapil Thangavelu]

Based on stopping an instance and restarting it. Will require work on txaws which doesn't support these operations atm.

[Gustavo Niemeyer (niemeyer)]

We have to be careful when doing this. Right now we have the one-unit-per-machine concept, but this
is not our end goal. A single machine may hold multiple services and multiple units, so stopping a service
is not simply shutting down a machine.

[Kapil Thangavelu (hazmat)]

good point, we'll need additional facilities around persistent data then to enable on a non machine basis.

[Kapil Thangavelu (hazmat)]

Alternatively this is still a useful notion on an environment level, .. prototype an environment freeze it, go to sleep ;-), wake up and restore. The notion of restoring transient connections as expressed in relations requires some thought. For client/server, bringing up servers before clients would do. Its not clear if we want to repeat events here, esp. as relation establishment sometimes begets resource allocation. Requires some more thought and brainstorming.