Allow microdroid_manager to set dev.bootcomplete

... and shell to get the same property for testing.

Bug: 230774156
Test: atest MicrodroidTestCase
Change-Id: Iaf04072c2b394d44ef1253fd048d5ccf757a8b89
diff --git a/microdroid/system/private/property.te b/microdroid/system/private/property.te
index 01aa5e4..abb193f 100644
--- a/microdroid/system/private/property.te
+++ b/microdroid/system/private/property.te
@@ -1,3 +1,5 @@
+system_restricted_prop(boot_status_prop)
+
 # Declare ART properties for CompOS
 system_public_prop(dalvik_config_prop)
 system_restricted_prop(device_config_runtime_native_prop)