Maybe try more than once if a connection timed out?

I tried to make sense of recent emma runs in Uganda (see tpo/community/outreach#40007 (closed)) and noticed that it's difficult to tell if a connection failed because of reliability issues or because of censorship. Emma currently tries once to establish a TCP connection to a target and if that fails, it labels the target as unreachable. It's up to the operating system to determine the number of TCP retransmissions. Let's teach emma to try more than once to establish a TCP connection to a target. This will increase the test time a little bit but I think the improved clarity is worth the additional wait time.