Fixes some issues encountered by our users.
- Restarting a peer could leave stale entries in WeaveDNS #1867/#2023/#2081
- Weave proxy occasionally failing to attach any new containers #2016/#2049
Other fixes:
- Resolved a crash when a restarting peer re-connected to a peer that had not received the latest IPAM data #2083/#2092
- Make IP address space available immediately after a dead peer is removed #2068
