Fix issues with CTF parser.

Fix issues with CTF parser.

* When an enum is declared in a different scope than it is defined in.
* When there is no stream ID the trace does not generate NPEs.
* When there is no clock offset, a 0 offset is created. (not often)

Change-Id: Ie0e0e09168aa2d91ac52d49e94bc10e1e9ba691f
Signed-off-by: Matthew Khouzam <matthew.khouzam@ericsson.com>
Reviewed-on: https://git.eclipse.org/r/6949
Reviewed-by: Patrick Tasse <patrick.tasse@gmail.com>
IP-Clean: Patrick Tasse <patrick.tasse@gmail.com>
Tested-by: Patrick Tasse <patrick.tasse@gmail.com>