Fix build warnings

This commit fixes some build warnings in CI caused by unused variables
and an invalid move assignment operator, since a member variable is of
reference type.

Signed-off-by: John Wedig <johnwedig@google.com>
Change-Id: I2b813ef017e47f2d35666063435a52638b74d156
diff --git a/include/estoraged.hpp b/include/estoraged.hpp
index c938c33..42d60f3 100644
--- a/include/estoraged.hpp
+++ b/include/estoraged.hpp
@@ -63,7 +63,7 @@
     EStoraged& operator=(const EStoraged&) = delete;
     EStoraged(const EStoraged&) = delete;
     EStoraged(EStoraged&&) = default;
-    EStoraged& operator=(EStoraged&&) = default;
+    EStoraged& operator=(EStoraged&&) = delete;
 
     /** @brief Format the LUKS encrypted device and create empty filesystem.
      *