Stop respawning serial console if disabled

After introducing ro.boot.serialconsole=0, the console will no longer be
spawned, but a step was missed to disable the service to prevent
respawns.

Bug: 266982931
Bug: 223797063
Bug: 267428635
Change-Id: I12b159eaa1999781aec31c05ce431b55e2ba4017

init/service.cpp

@@ -453,6 +453,7 @@ Result<void> Service::CheckConsole() {
     // disable services requiring the console. For older kernels and boot
     // images, not setting this at all will fall back to the old behavior
     if (GetProperty("ro.boot.serialconsole", "") == "0") {
+        flags_ |= SVC_DISABLED;
         return {};
     }