test(rust): pin disk counter restart after a fractional value

Co-Authored-By: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>

litellm-rust/crates/cache-disk/tests/cache.rs

@@ -231,6 +231,12 @@ fn counters_use_atomic_native_values_and_ignore_invalid_initial_values() {
             .unwrap(),
         "real"
     );
+    assert_eq!(
+        cache
+            .increment_cache("counter", 1.0, ExactCacheContext::default())
+            .unwrap(),
+        1.0
+    );
 }
 
 #[test]