util: remove a unnecessary check

We only break out of the previous loop if fd >= 0 so there is no
use in checking it again.

Found by coverity. Fixes: CID#1237577

src/shared/util.c

@@ -1878,9 +1878,6 @@ int open_terminal(const char *name, int mode) {
                 c++;
         }
 
-        if (fd < 0)
-                return -errno;
-
         r = isatty(fd);
         if (r < 0) {
                 safe_close(fd);