libsnapshot: update resume offset calculation

Update resume offset calculation to use function call

Test: cow_api_test
Change-Id: I7a9a86dc007110d02d889d1e59b24c3068b8d9e9
diff --git a/fs_mgr/libsnapshot/libsnapshot_cow/parser_v3.cpp b/fs_mgr/libsnapshot/libsnapshot_cow/parser_v3.cpp
index 52c6348..8e0f190 100644
--- a/fs_mgr/libsnapshot/libsnapshot_cow/parser_v3.cpp
+++ b/fs_mgr/libsnapshot/libsnapshot_cow/parser_v3.cpp
@@ -79,7 +79,7 @@
 
     return android::base::ReadFullyAtOffset(fd, resume_points_->data(),
                                             header_.resume_point_count * sizeof(ResumePoint),
-                                            header_.prefix.header_size + header_.buffer_size);
+                                            GetResumeOffset(header_));
 }
 
 std::optional<uint32_t> CowParserV3::FindResumeOp(const uint64_t label) {