Return true from extend_thin_meta_device less

Return true only if the method returned without error AND the amount to
extend is non-zero.

This is the same condition already used in extend_thin_data_device.

Signed-off-by: mulhern <[email protected]>

src/engine/strat_engine/thinpool/thinpool.rs

@@ -1117,7 +1117,10 @@ impl ThinPool {
                 meta_growth,
             );
 
-            (ext.is_ok(), ext)
+            match ext {
+                Ok(Sectors(0)) | Err(_) => (false, ext),
+                Ok(_) => (true, ext),
+            }
         } else {
             (false, Ok(Sectors(0)))
         }