Call drreg_restore_all prior to clean calls

In order for clean calls to have access to a machine context that contains original register/flag values, we need to call drreg's drreg_restore_all(). Essentially, the issue is that due to drreg's lazy restoration, registers may not have their original values upon invoking a clean call.

drreg_restore_app_values() is not appropriate as it only works on a passed operand.