SSU2: Peer test improvements

- Return OK as Alice when only receiving msg 5, unless snatted (SSU 1 also)
- Allow and handle firewalled Charlie as Alice
- Only create peer test data once as Alice
- Store test status and send-to-Alice time in test state to support retransmission
- Don't delete state after sending msg 4 as Bob, for possible retransmission
- Check for IP mismatch from Charlie as Alice, abort test and assume good
- Check for port mismatch from Charlie as Alice and validate
- Skip unroutable addresses when searching through RI for the right one
- Respond to retransmitted msg 1 as Bob
- Respond to retransmitted msg 2 as Charlie
- Update Charlie timer to retransmit msg 5
- Only send Charlie RI to Alice (as Bob) if test was accepted
- Convert timers to SimpleTimer2 (SSU 1 also)
- Log tweaks