Fix CID 1534938 (COPY_INSTEAD_OF_MOVE)

Signed-off-by: Stefan Weil <sw@weilnetz.de>

src/ccutil/unicity_table.h

@@ -80,7 +80,7 @@ public:
   int push_back(T object)  {
     auto idx = get_index(object);
     if (idx == -1) {
-      idx = table_.push_back(object);
+      idx = table_.push_back(std::move(object));
     }
     return idx;
   }