Only reduce polling rate for likely done streamer

There are at most two active streamer which are not considered "likey done" at a time. Not reducing their polling rate decreases processing delays.
Also increase the default delay on error as this now only applies to
exceptional cases.

src/AsapoWorker/streamer.py

@@ -19,7 +19,7 @@ def has_newer_substream(substream, substream_list):
 
 class Streamer:
     def __init__(
-            self, receiver, worker, delay_on_error=1,
+            self, receiver, worker, delay_on_error=3,
             end_of_stream_callback=None):
         self.receiver = receiver
         self.worker = worker
@@ -122,7 +122,7 @@ class Streamer:
         try:
             while not self.stopped.is_set():
                 success = self._process_stream()
-                if not success:
+                if self.likely_done and not success:
                     self.stopped.wait(self.delay_on_error)
                     self._increase_delay_on_error()
                 else: