hwclock: do not create a zero adjfile

When hwclock --hctosys is started very early during the system startup,
with / still mounted read-only, and there was no /etc/adjtime file,
hwclock fails creating a default adjfile full of zeroes, and prints an
error message. I believe that such zero adjfile is not necessary,
because it means exactly the same as no adjfile at all.

The attached patch prevents creation of a zero adjfile, of course unless
something gets changed (this never happens during a --hctosys).

Signed-off-by: Alain Guibert <alguibert+ulng@free.fr>

hwclock/hwclock.c

@@ -257,6 +257,7 @@ read_adjtime(struct adjtime *adjtime_p) {
       adjtime_p->not_adjusted = 0;
       adjtime_p->last_calib_time = 0;
       adjtime_p->local_utc = UNKNOWN;
+      adjtime_p->dirty = FALSE;        /* don't create a zero adjfile */
 
       return 0;
     }