fmt_addr used more than once in parameter lists

fmt_addr is called twice as an argument to log_notice, in two places in transport_resolve_conflicts. Maybe other places too. Because fmt_addr writes to a static buffer, one call clobbers the result of the other.

With this torrc,

ClientTransportPlugin dummy socks4 1.1.1.1:10001
ClientTransportPlugin dummy socks4 2.2.2.2:10001
Log "notice stderr"

you get the log (observe wrongly repeated address)

[notice] You tried to add transport 'dummy' at '2.2.2.2:10001' but the same transport already exists at '2.2.2.2:10001'. Skipping.