config: Bugfix: Don't skip unseen opcodes

libssh fails to read the configuration from a config file due to a
wrong check in 'ssh_config_parse_line' procedure in 'config.c'; it's
effectively skipping every opcode (and therefore every option) from
the file.  The change fixes that behaviour.

Signed-off-by: Artyom V. Poptsov <poptsov.artyom@gmail.com>
Reviewed-by: Andreas Schneider <asn@cryptomilk.org>

src/config.c

@@ -219,7 +219,7 @@ static int ssh_config_parse_line(ssh_session session, const char *line,
 
   opcode = ssh_config_get_opcode(keyword);
   if (*parsing == 1 && opcode != SOC_HOST) {
-      if (seen[opcode] == 0) {
+      if (seen[opcode] != 0) {
           return 0;
       }
       seen[opcode] = 1;