Correct help messages for image-update command
Correct help messages for image-update command

Currently when you are trying to update the location of an image which
is not in queued status you will get an error from the Glance API. The
help message for --location and --copy-from arguments should be updated
to inform the user that it works only for images in queued status.

Co-Authored-By: Abhishek Talwar <abhishek.talwar@tcs.com>
Co-Authored-By: Kamil Rykowski <kamil.rykowski@intel.com>

Change-Id: I82b14ffde3f301d7ffef68e984ba4ad2ae0f8b0f
Closes-Bug: #1220809

mmasaki/python-glanceclient,JioCloud/python-glanceclient,varunarya10/python-glanceclient,openstack/python-glanceclient,JioCloud/python-glanceclient,klmitch/python-glanceclient,klmitch/python-glanceclient,openstack/python-glanceclient,varunarya10/python-glanceclient,mmasaki/python-glanceclient