init: Let property_get return std::string.

Bug: 22654233

Change-Id: Id6091f58432f75e966b9871256049fbe17766c10
diff --git a/init/builtins.cpp b/init/builtins.cpp
index 8d47da4..e2c033a 100644
--- a/init/builtins.cpp
+++ b/init/builtins.cpp
@@ -920,9 +920,8 @@
         return -1;
     }
 
-    char prop_value[PROP_VALUE_MAX] = {0};
-    property_get("ro.crypto.type", prop_value);
-    if (strcmp(prop_value, "file")) {
+    std::string prop_value = property_get("ro.crypto.type");
+    if (prop_value != "file") {
         return 0;
     }