fix(server): close SQLite stores in policy tests (#3466)

Signed-off-by: Kaylee Lubick <klubick@nvidia.com>

Author: kjlubick

crates/openshell-server/src/grpc/policy.rs

@@ -12101,6 +12101,9 @@ mod tests {
                 .unwrap()
                 .is_some()
         );
+
+        // Wait for SQLx's SQLite worker threads to stop before the test process exits;
+        state.store.close_for_test().await;
     }
 
     #[tokio::test]
@@ -14887,6 +14890,9 @@ mod tests {
                 .status,
             "approved"
         );
+
+        // Wait for SQLx's SQLite worker threads to stop before the test process exits;
+        state.store.close_for_test().await;
     }
 
     #[tokio::test]
@@ -18770,6 +18776,9 @@ mod tests {
             "undo must clear stale rejection_reason; got: {:?}",
             restored.rejection_reason
         );
+
+        // Wait for SQLx's SQLite worker threads to stop before the test process exits;
+        state.store.close_for_test().await;
     }
 
     #[tokio::test]
@@ -18954,6 +18963,9 @@ mod tests {
         .await
         .unwrap_err();
         assert_eq!(undo_err.code(), Code::NotFound);
+
+        // Wait for SQLx's SQLite worker threads to stop before the test process exits;
+        state.store.close_for_test().await;
     }
 
     #[test]