Fix linking with openssl with disable sslv2 (e.g. debian)

On debian and probably also on other linux distributions, linking fails with the following error:

- linking noitd
noit-objs/eventer/eventer_SSL_fd_opset.o: In function `eventer_ssl_ctx_new':
/opt/reconnoiter/source/src/eventer/eventer_SSL_fd_opset.c:541: undefined reference to `SSLv2_server_method'
/opt/reconnoiter/source/src/eventer/eventer_SSL_fd_opset.c:541: undefined reference to `SSLv2_client_method'
collect2: error: ld returned 1 exit status

This is because openssl is compiled without SSLv2 and the #ifdef fails to isolate the affected code.
This adds an additional #ifndef on OPENSSL_NO_SSL2 like specified in <openssl/ssh.h>.