Allow vold to deleteAllKeys in Keystore

Add deleteAllKeys to IKeystoreMaintenance and allow vold to call it.
Allow vold to read the property
`ro.crypto.metadata_init_delete_all_keys.enabled`

Bug: 187105270
Test: booted twice on Cuttlefish
Change-Id: I2fb0e94db9d35c1f19ca7acb2f541cfb13c23524
diff --git a/private/access_vectors b/private/access_vectors
index 3732a52..6edcd1f 100644
--- a/private/access_vectors
+++ b/private/access_vectors
@@ -731,6 +731,7 @@
 	report_off_body
 	reset
 	unlock
+	delete_all_keys
 }
 
 class keystore2_key