Adding dry_run flag for salt.control state

Issue: on virtual environments where nested virtualization is not
       possible, we cannot get config drive iso files

Solution: generate config dirve isoes by running salt.control
          state with dry_run=True

As for comment in the code, I prefer to switch from start=True to
dry_run=False and switch to it.
This is why I added new flag. Product team can switch on the fly
and deprecate start=True usage

Prod-Related: PROD-29586

Change-Id: I2e5485e3e2a4fec06edc874de12fd50fb76d8264
2 files changed