release-script: fix little release_pip glitch

after release_pip the script would init another release which
is not wanted.

Author: aoeftiger

release.py

@@ -407,9 +407,10 @@ def release_pip():
     # are we on a release branch already?
     if not (current_branch()[:len(release_branch_prefix)] ==
             release_branch_prefix):
-        args = parser.parse_args()
         if current_branch() == 'master':
             release_pip()
-        init_release(args.part)
+        else:
+            args = parser.parse_args()
+            init_release(args.part)
     else:
         finalise_release()