Fix: relayd: missing metadata stream causes all traces to be skipped

Fix: relayd: missing metadata stream causes all traces to be skipped

Commit 123ed7c22 intends for a trace that doesn't have a metadata
stream to be skipped when creating viewer streams. However, the loop
over ctf_traces should be "continued" rather then "broken" from when
this situation arises. Otherwise, all ctf_traces of the session are
skipped, which is not the intention here.

Moreover, a reference to the current ctf_trace is leaked when the
break (now continue) occurs.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Change-Id: Ic630521c6f050c77a78f2c1e20c5741a6b3a66a1