fix index_received++ only after write

Signed-off-by: Julien Desfossez <jdesfossez@efficios.com>
Match ctf_traces

Introduce a new per-connection HT indexed by path_name and accepting
duplicate keys.
When a new metadata stream arrives, we create a new ctf_trace struct,
assign it a unique ID and match all streams with the same path to this
ctf_trace.

Signed-off-by: Julien Desfossez <jdesfossez@efficios.com>