tmf: Bug 509691: Changes to mutable trace context can be lost

tmf: Bug 509691: Changes to mutable trace context can be lost

The method TmfTraceManager.updateTraceContext() is now used to apply all
changes to a trace context under synchronization of the trace manager.

Change-Id: Id8cecd92c7f7c4c7203d965ce7fb36a6fed74626
Signed-off-by: Patrick Tasse <patrick.tasse@gmail.com>
Reviewed-on: https://git.eclipse.org/r/87711
Reviewed-by: Hudson CI
Reviewed-by: Matthew Khouzam <matthew.khouzam@ericsson.com>
Tested-by: Matthew Khouzam <matthew.khouzam@ericsson.com>