When variable names are put in observables in VOCS Xopt complaints

[wenatuhs]

Xopts seems to treat observables in VOCS as pure "observables" in Badger env -- meaning that it fetches the values by calling env.get_observables. But now we also want to support monitoring on variables, so either we:

• Add some logic in decorator on get_observables to allow it to fetch names in variable list
  • We might consider removing get_variables and merging the feature into get_observables, but it could be confusing to env devs
• Change logic in Routine a bit so that it calls the correct methods if get_observables fails.