manifestcache: stop altering the lru cache order while displaying it

Accessing value with `.get` alter the iteration order and make the output of
the debug command misbehave, showing multiple entry twice.

We need more than 2 entry to see the bug, so there are not test change. Later
test will introduce a third entry and would fail without this fix.

mercurial/debugcommands.py

@@ -1503,7 +1503,7 b' def debugmanifestfulltextcache(ui, repo,'
         totalsize = 0
         for nodeid in cache:
             # Use cache.get to not update the LRU order
-            data = cache.get(nodeid)
+            data = cache.peek(nodeid)
             size = len(data)
             totalsize += size + 24   # 20 bytes nodeid, 4 bytes size
             ui.write(_('id: %s, size %s\n') % (