Hi,
I ran into some tor restart loop issues after upgrading to 0.2.8.6 on my pi2 relay.
In short, it takes too long to read router_parse_list_from_string and hits the systemd start timeout limit causing a restart (and loop)
Full story in the ticket here: https://trac.torproject.org/projects/tor/ticket/19819
quick fix:
edit /lib/systemd/system/tor@default.service and change TimeoutStartSec= from 120 to 300
Hope i'm not "spamming" the list, just trying to help.
Have a good one.