set_ub_dns_transport() not working

[johndickinson]

I have been checking some stuff with wireshark and everything appears to go over UDP regardless of the the transport set in getdns_context_set_dns_transport();

This appears to be due to missing :'s in the six calls to set_ub_string_opt() in set_ub_dns_transport.
The current code reads:
set_ub_string_opt(context, "do-tcp", "yes");
it should read
set_ub_string_opt(context, "do-tcp:", "yes");

See http://unbound.net/documentation/libunbound.html

I will do a PR once I figure out a nice way to test the actual transport used. Please shout if this is me doing something stupid!