Set a property if seed binding is enabled.

For vehicle binding seed atest

Bug: 157501579
Test: atest vehicle-binding-seed-sh
Change-Id: Ie1dad1735193ce722ec036e38f826a6b90e94526
diff --git a/KeyStorage.cpp b/KeyStorage.cpp
index 6aab4bd..ebaefa3 100644
--- a/KeyStorage.cpp
+++ b/KeyStorage.cpp
@@ -712,6 +712,7 @@
         case StorageBindingInfo::State::UNINITIALIZED:
             storage_binding_info.state = StorageBindingInfo::State::IN_USE;
             storage_binding_info.seed = seed;
+            android::base::SetProperty("vold.storage_seed_bound", "1");
             return true;
         case StorageBindingInfo::State::IN_USE:
             LOG(ERROR) << "key storage binding seed already set";