refine test TestIpfwdEnableDisableStatusForwarding and some minor changes on test

1. fix flaky test for TestIpfwdEnableDisableStatusForwarding
2. fix time unit error in binder_test, set retry default
   interval as 50ms
3. refine naming in binder_test

Bug: 128533612
Test: built, flashed, booted
      system/netd/tests/runtests.sh pass

Change-Id: Ia03d0c30b49cdd233b627cce8bd2f3f05548798e
diff --git a/server/TetherController.h b/server/TetherController.h
index 49c2339..0a04874 100644
--- a/server/TetherController.h
+++ b/server/TetherController.h
@@ -71,7 +71,7 @@
 
     bool enableForwarding(const char* requester);
     bool disableForwarding(const char* requester);
-    size_t forwardingRequestCount();
+    const std::set<std::string>& getIpfwdRequesterList() const;
 
     int startTethering(int num_addrs, char **dhcp_ranges);
     int startTethering(const std::vector<std::string>& dhcpRanges);