Automatic merge from submit-queue

Remove unused method from operation_generator

This is only a removal of the GerifyVolumeIsSafeToDetach [sic] method from operation_executor. The method is not called from anywhere, moreover there is a private method named verifyVolumeIsSafeToDetach (which is being used). This looks like a cut&paste mistake that deserves to be cleaned.
```release-note
NONE
```