Hook the AuthManger#modify_user method into nova-manage commands.

bin/nova-manage

@@ -228,6 +228,19 @@ class UserCommands(object):
         for user in self.manager.get_users():
             print user.name
 
+    def modify(self, name, access_key, secret_key, is_admin):
+        """update a users keys & admin flag
+        arguments: accesskey secretkey admin
+        leave any field blank to ignore it, admin should be 'T', 'F', or blank
+        """
+        if not is_admin:
+            is_admin = None
+        elif is_admin.upper()[0] == 'T':
+            is_admin = True
+        else:
+            is_admin = False
+        print "is_admin: %r" % is_admin
+        self.manager.modify_user(name, access_key, secret_key, is_admin)
 
 class ProjectCommands(object):
     """Class for managing projects."""