Fix an fd leak in check_private_dir().

The fd would leak when the User wasn't recogniezed by
getpwnam(). Since we'd then go on to exit, this wasn't a terribad
leak, but it's still not as nice as no leak at all.

CID 1355640; bugfix on no released Tor.

src/common/util.c

@@ -2157,6 +2157,7 @@ check_private_dir(const char *dirname, cpd_check_t check,
     if (pw == NULL) {
       log_warn(LD_CONFIG, "Error setting configured user: %s not found",
                effective_user);
+      close(fd);
       return -1;
     }
     running_uid = pw->pw_uid;