Regex matching throws exception in Pair

[Rupak Majumdar]

When using hold with regular expressions, Pair throws an exception because it expects the two IpAddr to be different.
Here is a minimal test:

    #[test] 
    #[cfg(feature = "regex")]
    fn hold_all() -> Result {
        let mut sim = Builder::new().build();

        sim.host("host", || { async { future::pending().await } });
        sim.client("client", async {  
                hold(regex::Regex::new(r".*")?, regex::Regex::new(r".*")?);
                Ok(())
        });
    
        sim.run()?;
        Ok(())
    }

Fails with:

thread 'sim::test::hold_all' panicked at 'assertion failed: `(left != right)`
  left: `192.168.0.1`,
 right: `192.168.0.1`', src/top.rs:35:9
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
thread 'sim::test::hold_all' panicked at 'a spawned task panicked and the LocalSet is configured to shutdown on unhandled panic', /Users/foo/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-1.26.0/src/task/local.rs:603:17