Client management zeros out client grace period

[jjg-123]

The client management endpoint is not handling the grace period for the client. Meaning, it is neither sent nor updated. This means that updates to client would reset it to the database default which is 0, meaning it disables the grace period for that client. The net effect is that on refresh, any token would be invalidated immediately.

This is a reasonable explanation for issues we have been having, (e.g. https://jira.ncsa.illinois.edu/browse/CIL-1842) viz., ever more clients seem to be affected and there is not a clear pattern to it. However, it is not a smoking gun, but should be fixed.