Fix seed with multiple runs (#1138)

* Fix seed with multiple runs

* addressed comments

ml-agents/mlagents/learn.py

     num_runs = int(options['--num-runs'])
     seed = int(options['--seed'])
 
-    if options['--env'] != 'None' and num_runs > 1:
+    if options['--env'] == 'None' and num_runs > 1:
+    run_seed = seed
-            seed = np.random.randint(0, 9999)
-        p = multiprocessing.Process(target=run_training, args=(i, seed, options))
+            run_seed = np.random.randint(0, 10000)
+        p = multiprocessing.Process(target=run_training, args=(i, run_seed, options))
         jobs.append(p)
         p.start()