Lower severity of getBootstrapPeer failure when it has no UDP answer

It's normal such failure happens occasionally and re6st retries later so:
- do not frighten user/admin with 500 status and ssl errors
- do not waste resources by killing session with registry

re6st/db.py

@@ -102,7 +102,8 @@ class PeerDB(object):
             bootpeer = self._registry.getBootstrapPeer(self._prefix)
             prefix, address = utils.decrypt(self._key_path, bootpeer).split()
         except (socket.error, subprocess.CalledProcessError, ValueError), e:
-            logging.warning('Failed to bootstrap (%s)', e)
+            logging.warning('Failed to bootstrap (%s)',
+                            e if bootpeer else 'no peer returned')
         else:
             if prefix != self._prefix:
                 self.addPeer(prefix, address)

re6st/registry.py

@@ -271,8 +271,8 @@ class RegistryServer(object):
                         break
                 timeout = max(0, time.time() - start)
             else:
-                raise EnvironmentError("Timeout while querying [%s]:%u"
-                                       % address)
+                logging.info("Timeout while querying [%s]:%u", *address)
+                return
         logging.info("Sending bootstrap peer: %s", msg)
         return utils.encrypt(cert, msg)