VTS gets vbmeta open error due to open_partition() is called with O_WRONLY

Bug: 293489415
Test: run vts -m vts_security_avb_test -t AvbTest#HashtreeAlgorithm

Signed-off-by: Kilyoung Shin <gilbert.shin@samsung.com>
(cherry picked from https://android-review.googlesource.com/q/commit:44b7409468568836097c8544ab024b25074ff21d)
Merged-In: I911b5b992a861431a9359f84bc9494ebdaf5a9ad
Change-Id: I911b5b992a861431a9359f84bc9494ebdaf5a9ad
diff --git a/libavb_user/avb_ops_user.cpp b/libavb_user/avb_ops_user.cpp
index 1ce5391..451dff2 100644
--- a/libavb_user/avb_ops_user.cpp
+++ b/libavb_user/avb_ops_user.cpp
@@ -270,7 +270,7 @@
   int fd;
   AvbIOResult ret;
 
-  fd = open_partition(partition, O_WRONLY);
+  fd = open_partition(partition, O_RDONLY);
   if (fd == -1) {
     avb_error("Error opening \"", partition, "\" partition.\n");
     ret = AVB_IO_RESULT_ERROR_IO;