Remove the live attribute and mark the definition as transient
whether the domain is runing or not.

There were only two callers left calling with live=false:
* testDomainStartState, where the domain already is active
  because we assigned vm->def->id just a few lines above the call
* virDomainObjGetPersistentDef, which now only calls
  virDomainObjSetDefTransient for an active domain