hwclock: always set the kernel's timezone

Properly tell the kernel at bootup, and any later time zone changes,
the actual system time zone.

Things like the kernel's FAT filesystem driver needs the actual time
zone to calculate the proper local time to use for the on-disk time
stamps.

https://bugzilla.redhat.com/show_bug.cgi?id=802198

src/shared/hwclock.c

@@ -188,7 +188,7 @@ int hwclock_is_localtime(void) {
         return local;
 }
 
-int hwclock_apply_localtime_delta(int *min) {
+int hwclock_set_timezone(int *min) {
         const struct timeval *tv_null = NULL;
         struct timespec ts;
         struct tm *tm;
@@ -214,13 +214,18 @@ int hwclock_apply_localtime_delta(int *min) {
         return 0;
 }
 
-int hwclock_reset_localtime_delta(void) {
+int hwclock_reset_timezone(void) {
         const struct timeval *tv_null = NULL;
         struct timezone tz;
 
         tz.tz_minuteswest = 0;
         tz.tz_dsttime = 0; /* DST_NONE*/
 
+        /*
+         * The very first time we set the kernel's timezone, it will warp
+         * the clock. Do a dummy call here, so the time warping is sealed
+         * and we set only the time zone with next call.
+         */
         if (settimeofday(tv_null, &tz) < 0)
                 return -errno;
 

src/shared/hwclock.h

@@ -23,8 +23,8 @@
 ***/
 
 int hwclock_is_localtime(void);
-int hwclock_apply_localtime_delta(int *min);
-int hwclock_reset_localtime_delta(void);
+int hwclock_set_timezone(int *min);
+int hwclock_reset_timezone(void);
 int hwclock_get_time(struct tm *tm);
 int hwclock_set_time(const struct tm *tm);