Fix: wrong loop continuation in metadata thread

The validation of the endpoint status can change the metadata hash table
meaning stream(s) can be removed from it and the poll set. After that,
continuing the for loop was making the thread use possible invalid file
descriptor that were not in the hash table anymore trigerring the lookup
assert of the node just after the for loop.

The very important part here is that when the metadata ht changes, we
MUST go back to the poll wait() to synchronize the subset of fd we are
looking at.

Reported-by: Jesus Garcia <jesus.garcia@ericsson.com>
Acked-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: David Goulet <dgoulet@efficios.com>