DHTPeerFinder: re-join the network if we have no peers

Periodically check if the routing table is empty and, if so,
re-attempt joining the DHT network.

This check is performed in the main DHTPeerFinder loop every 60 secs.

Closes: #1093
Signed-off-by: Antonio Quartulli <antonio@mandelbit.com>

CHANGELOG.md

@@ -40,6 +40,7 @@ at anytime.
   * Remove manual saving of the wallet in from lbrynet, let lbryum handle it
   * Block wallet startup on being unlocked if it is encrypted
   * Use reworked lbryum payto command
+  * Re-attempt joining the DHT every 60 secs if the Node has no peers
 
 ### Added
   * Add link to instructions on how to change the default peer port

lbrynet/core/client/DHTPeerFinder.py

@@ -34,8 +34,15 @@ class DHTPeerFinder(object):
             self.next_manage_call.cancel()
             self.next_manage_call = None
 
+    @defer.inlineCallbacks
     def _manage_peers(self):
-        pass
+        """
+        If we don't know any active peer, let's try to reconnect to the preconfigured
+        known DHT nodes
+        """
+        if not self.dht_node.hasContacts():
+            log.info("No active peer. Re-attempt joining DHT")
+            yield self.dht_node.join_dht()
 
     @defer.inlineCallbacks
     def find_peers_for_blob(self, blob_hash, timeout=None, filter_self=False):