urlOpen: Set errno to ENOENT on error

Callers use the errno for error reporting. Currently it is set to ENOENT
by accident bubbling up from rpmMkTempFile and rpmioMkpath.

As we need to change rpmioMkpath set errno explicitly to keep the errno
the same for the callers of urlOpen.

Related: #3508

Author: ffesti

rpmio/rpmio.cc

@@ -462,6 +462,7 @@ static FD_t urlOpen(const char * url, int flags, mode_t mode)
 	unlink(dest);
     } else {
 	fd = NULL;
+	errno = ENOENT;
     }
     dest = _free(dest);