politeiavoter: Does not recover from failed attempt

[davecgh]

While using the --voteduration option to trickle votes, politeiavoter periodically encounters an error, probably due to transient network issues, particularly because it is typically done over Tor when trickling, and exits instead of retrying.

unrecoverable error: Post https://test-proposals.decred.org/api/v1/proposals/castvotes: EOF

When combined with the other issues as described in #562 and #565, this makes it extremely difficult to actually use without manually modifying the code after each error to manually skip tickets.

[raedah]

Same same, requires manual restart. Expected behavior is automatic recovery.

[lukebp]

Closed by #639.

[jzbz]

Still get unrecoverable error: 504 periodically on 1.4. Restarting picks things up from where they left off. No useful info in politeiavoter.log.

[davecgh]

Same. I suspect something has changed since #639 that broke it again.

[davecgh]

I opened #713 to track the 504 gateway timeout issue.