dig hangs when there is a TLS context creation failure

For testing, you can simulate an error by providing TLS certificate file without a key. This will hang in main until interrupted:

bin/dig/dig +tcp +tls +tls-certfile=/dev/null localhost
;; both TLS client certificate and key file must be specified a the same time
^C

There seems to be a missing detachment of the connectquery in dighost.c:start_tcp() when get_create_tls_context() call fails.

Assigning to @artem by his request.