init: make reboot_on_failure not apply to manually stopped services

Add a new service flag SVC_STOPPING which tracks whether a service is
being manually stopped by init, and make the "reboot_on_failure" service
setting not apply when SVC_STOPPING is set.

This is needed for devices that use FDE, because otherwise the device
reboots during the following init script fragment:

    on property:vold.decrypt=trigger_shutdown_framework
        class_reset late_start
        class_reset main
        class_reset_post_data core
        class_reset_post_data hal

... because that stops all services, including apexd which has been
marked with reboot_on_failure since
https://android-review.googlesource.com/c/platform/system/apex/+/1325212.
So init was killing apexd, then rebooting the device because apexd
"failed" due to having been killed.  Making reboot_on_failure not apply
when init stops a service itself fixes the problem.

This is one of a set of changes that is needed to get FDE working again
so that devices that launched with FDE can be upgraded to Android 12.

Bug: 186165644
Test: Tested FDE on Cuttlefish
Change-Id: I599f7ba107e6c126e8f31d0ae659f0ae672a25e4
diff --git a/init/service.h b/init/service.h
index 043555f..89b1f09 100644
--- a/init/service.h
+++ b/init/service.h
@@ -54,6 +54,7 @@
                                      // should not be killed during shutdown
 #define SVC_TEMPORARY 0x1000  // This service was started by 'exec' and should be removed from the
                               // service list once it is reaped.
+#define SVC_STOPPING 0x2000  // service is being stopped by init
 
 #define NR_SVC_SUPP_GIDS 12    // twelve supplementary groups