fix lax service context lookup

Inform checkfc about new service label backend.

Test: bullhead builds

Bug: 31353148
Change-Id: I499da36108e67483a4f9a18fd8cc7c8f13419abd
diff --git a/tools/checkfc.c b/tools/checkfc.c
index e7d19b0..8a28f3c 100644
--- a/tools/checkfc.c
+++ b/tools/checkfc.c
@@ -346,7 +346,7 @@
         break;
       case 's':
         mode = filemode_service_contexts;
-        backend = SELABEL_CTX_ANDROID_PROP;
+        backend = SELABEL_CTX_ANDROID_SERVICE;
         break;
       case 'h':
       default: