Bug 9060: Remove un-used Instant getObjectCreated() from CloseTracked

Bug 9060: Remove un-used Instant getObjectCreated() from CloseTracked

I initially thought that it would be "interesting" to be able to do some
sort of output sorted by the age of the object creating kind of UX in
the CLI I'm planning to propose next, but ultimately realized that
keeping an extra Instant fields in EACH CloseTracked (e.g. Tx) is just
overhead and not really adding much value (because the NUMBER of
non-closed objects is MUCH more interesting than this timestamp..), thus
removing this again after all.

This is one of a serious of commits which is part of a solution I'm
proposing in order to be able to detect OOM issues such as Bug 9034,
based on using the mdsal-trace DataBroker.

Change-Id: Ie40fe23ce2af670902ff8e44a6757ebdf9ef915e
Signed-off-by: Michael Vorburger <vorburger@redhat.com>