ctf: Attempt to gracefully recover from a malformed packet context

ctf: Attempt to gracefully recover from a malformed packet context

If a packet context has an end time that is less than the start time
tracecompass will give an error message and refuse to read the trace.

This patch makes tracecompass log a warning instead and try to read
the trace.

Seeking should not be affected.

Bug 486670

Change-Id: I352af4c79476c73b0ced2cefd65f82bd04d6762d
Signed-off-by: Matthew Khouzam <matthew.khouzam@ericsson.com>
Reviewed-on: https://git.eclipse.org/r/65168
Reviewed-by: Bernd Hufmann <bernd.hufmann@ericsson.com>
Tested-by: Bernd Hufmann <bernd.hufmann@ericsson.com>
Reviewed-by: Hudson CI