main: cancel clock correction before dumping sources

On exit, cancel the remaining clock correction before measurements are
saved to dumpdir to fix them for the state in which chronyd will start
again.

main.c

@@ -104,6 +104,7 @@ MAI_CleanupAndExit(void)
 {
   if (!initialised) exit(exit_status);
   
+  LCL_CancelOffsetCorrection();
   SRC_DumpSources();
 
   /* Don't update clock when removing sources */