Remove duplicated marker id dump

Remove duplicated marker id dump

Marker ID is already dumped at:
- trace start (with marker dump)
- when a marker is enabled (probe callback associated with marker).

So this should cover all cases:
- either we have a marker in a lib/program that is already enabled, and start
  tracing after a library is loaded, for which the marker dump will catch the
  marker id.
- or we have a marker in a lib/program that is not enabled, and start tracing
  after a library is loaded. If after that we enable the marker, an event
  describing the marker ID will be generated.
- or if have tracing running, and then we enable a marker (connect probe to
  marker) for a marker located in a yet-unloaded library. In this case, the
  marker ID event is generated when we connect the probe to the marker, even if
  the library is not yet loaded.

The cases are similar for the marker format, except that it is valid to have an
unknown marker format when we connect a marker probe. In that case, the format
will be written into the trace by marker_set_format, called upon library load.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>