Modify the usage section of Config Manager README.md
Modify the usage section of Config Manager README.md

Change-Id: Ic1709a7bd6d56ae8b063aaceff3639726cb06769

GoogleCloudPlatform/esp-v2,GoogleCloudPlatform/esp-v2,GoogleCloudPlatform/esp-v2,GoogleCloudPlatform/esp-v2,GoogleCloudPlatform/esp-v2