Problem: zyre_log.c:121: zyre_log_info: Assertion `self' failed.
Problem: zyre_log.c:121: zyre_log_info: Assertion `self' failed.

Caused when sending JOIN/LEAVE commands to a node that isn't yet
started (so has no logger).

Solution: do not try to log these commands if the node wasn't
started yet.

Fixes #197.

c-rack/zyre,awynne/zyre,trevorbernard/zyre,zoobab/zyre,trevorbernard/zyre,hintjens/zyre,hintjens/zyre,c-rack/zyre,zoobab/zyre,keent/zyre,Asmod4n/zyre,twhittock/zyre,Asmod4n/zyre,trevorbernard/zyre,hintjens/zyre,awynne/zyre,zoobab/zyre,zeromq/zyre,c-rack/zyre,keent/zyre,twhittock/zyre,keent/zyre,trevorbernard/zyre,hintjens/zyre,zeromq/zyre,awynne/zyre,zeromq/zyre,awynne/zyre,twhittock/zyre,zeromq/zyre,Asmod4n/zyre,zeromq/zyre,zoobab/zyre,awynne/zyre,awynne/zyre,trevorbernard/zyre,zoobab/zyre,zoobab/zyre,zoobab/zyre,Asmod4n/zyre,keent/zyre,hintjens/zyre,twhittock/zyre,twhittock/zyre,twhittock/zyre,zoobab/zyre,trevorbernard/zyre,zeromq/zyre,hintjens/zyre,twhittock/zyre,c-rack/zyre,hintjens/zyre,Asmod4n/zyre,keent/zyre,zeromq/zyre,hintjens/zyre,c-rack/zyre,zeromq/zyre,keent/zyre,twhittock/zyre,c-rack/zyre,Asmod4n/zyre