Schematize vold system properties

Properties accessed across partitions are now schematized and will
become APIs to make explicit interfaces among partitions.

Bug: 117924132
Test: m -j
Change-Id: I8e04f643197b6c8a60cc38c6979e41c5de3469f5
(cherry picked from commit 0cf5fc1433ef113d33d40b62cfca9ce97de12a4b)
diff --git a/services/java/com/android/server/SystemServer.java b/services/java/com/android/server/SystemServer.java
index e364e9a..e62186a 100644
--- a/services/java/com/android/server/SystemServer.java
+++ b/services/java/com/android/server/SystemServer.java
@@ -55,6 +55,7 @@
 import android.os.Trace;
 import android.os.UserHandle;
 import android.os.storage.IStorageManager;
+import android.sysprop.VoldProperties;
 import android.util.DisplayMetrics;
 import android.util.EventLog;
 import android.util.Slog;
@@ -655,7 +656,7 @@
         traceEnd();
 
         // Only run "core" apps if we're encrypting the device.
-        String cryptState = SystemProperties.get("vold.decrypt");
+        String cryptState = VoldProperties.decrypt().orElse("");
         if (ENCRYPTING_STATE.equals(cryptState)) {
             Slog.w(TAG, "Detected encryption in progress - only parsing core apps");
             mOnlyCore = true;