parse-util: make parse_fd() return -EBADF

The previous error code -ERANGE is slightly ambiguous, and use more
specific one. This also drops unnecessary error handlings.

Follow-up for 754d8b9c33 and
e652663a04.

src/basic/parse-util.c

@@ -343,7 +343,7 @@ int parse_fd(const char *t) {
                 return r;
 
         if (fd < 0)
-                return -ERANGE;
+                return -EBADF;
 
         return fd;
 }