snapuserd: Fix infinite loop when reading ops.

Bug: 168554689
Test: vts_libsnapshot_test
Change-Id: I48e62f258ef2b4c368e8237a132c802a03d7020b
diff --git a/fs_mgr/libsnapshot/snapuserd.cpp b/fs_mgr/libsnapshot/snapuserd.cpp
index 6e772ad..40f26d6 100644
--- a/fs_mgr/libsnapshot/snapuserd.cpp
+++ b/fs_mgr/libsnapshot/snapuserd.cpp
@@ -379,7 +379,11 @@
         struct disk_exception* de =
                 reinterpret_cast<struct disk_exception*>((char*)de_ptr.get() + offset);
 
-        if (cow_op->type == kCowFooterOp || cow_op->type == kCowLabelOp) continue;
+        if (cow_op->type == kCowFooterOp || cow_op->type == kCowLabelOp) {
+            cowop_iter_->Next();
+            continue;
+        }
+
         if (!(cow_op->type == kCowReplaceOp || cow_op->type == kCowZeroOp ||
               cow_op->type == kCowCopyOp)) {
             LOG(ERROR) << "Unknown operation-type found: " << cow_op->type;