iocInit: move dbCaShutdown earlier

Switch dbCaShutdown from an exit hook to
be called from iocShutdown.  Place it
after callback shutdown.

src/ioc/db/dbCa.c

@@ -223,19 +223,12 @@ void dbCaShutdown(void)
     }
 }
 
-static void dbCaExit(void *arg)
-{
-    dbCaShutdown();
-}
-
 void dbCaLinkInitIsolated(void)
 {
     if (!workListLock)
         workListLock = epicsMutexMustCreate();
-    if (!workListEvent) {
+    if (!workListEvent)
         workListEvent = epicsEventMustCreate(epicsEventEmpty);
-        epicsAtExit(dbCaExit, NULL);
-    }
     dbCaCtl = ctlExit;
 }
 

src/ioc/misc/iocInit.c

@@ -682,6 +682,9 @@ int iocShutdown(void)
         /* stop and "join" threads */
         scanStop();
         callbackStop();
+    }
+    dbCaShutdown();
+    if (iocBuildMode==buildIsolated) {
         /* free resources */
         scanCleanup();
         callbackCleanup();