cache_manage: fix a print bug in exit main

There is no output print format symbol %, add it and for
man exit, we should use sys.exit

Change-Id: I16cfded354a5a4a10c0524fd5b7cb9f4f9c9e6dd

glance/cmd/cache_manage.py

@@ -516,7 +516,7 @@ Commands:
             print("Completed in %-0.4f sec." % (end_time - start_time))
         sys.exit(result)
     except (RuntimeError, NotImplementedError) as e:
-        print("ERROR: ", e)
+        sys.exit("ERROR: %s" % e)
 
 if __name__ == '__main__':
     main()