use with-syntax for locks
- note flaky test
Change facilitator-test port from 9002 to 39002.

So as not to conflict with a production facilitator running on the same
host. Sniped from
"make tests work against the new interfaces"
https://github.com/infinity0/flashproxy/commit/a3a6b832c9d3db2b24251f09741ac34b92eafcd6
Factor out common code in returning logged errors.

Adapted from
"report more detailed errors and show stacktraces when unsafe logging"
https://github.com/infinity0/flashproxy/commit/c1af35b2e2d57cb8850b1cf345d29065766a9410
Remove FROM parameter in PUT commands.

It was planned to be used for source-based rate limiting, but was
unused. Adapted from
"Support new client registrations."
https://gitweb.torproject.org/user/asn/flashproxy.git/commitdiff/7b3010e1d4338d173bd9aec35e2ed819842d080d
"http registration: set default remote address properly - put_reg FROM is never actually read by facilitator"
https://github.com/infinity0/flashproxy/commit/4b8d3d65fbc78eca400e6c33e9987f923a7b18a1
"report more detailed errors and show stacktraces when unsafe logging"
https://github.com/infinity0/flashproxy/commit/c1af35b2e2d57cb8850b1cf345d29065766a9410
Fix a symbolic link in the drupal directory.

Broken since /modules moved to /proxy/modules.
Remove unused FACILITATOR_REG_URL_ADDR.

This was left over from when facilitator.cgi used to talk directly to
facilitator-reg-daemon (then called facilitator-reg-url).