Add Exponential LR scheduler check

TTS/bin/train_vocoder_gan.py

@@ -506,6 +506,8 @@ def main(args):  # pylint: disable=redefined-outer-name
                 print(" > Restoring Discriminator LR Scheduler...")
                 scheduler_disc.load_state_dict(checkpoint['scheduler_disc'])
                 scheduler_disc.optimizer = optimizer_disc
+                if c.lr_scheduler_disc == "ExponentialLR":
+                    scheduler_disc.last_epoch = checkpoint['epoch']
         except RuntimeError:
             # restore only matching layers.
             print(" > Partial model initialization...")