Kerberos requests fail if PING is blocked by firewall

[marius-klimantavicius]

Describe the bug
Exception after upgrading to latest version:

System.AggregateException: One or more errors occurred. (Ping xxxxxxxx returned TimedOut)
---> System.Net.NetworkInformation.PingException: Ping xxxxxxxx returned TimedOut
at Kerberos.NET.Transport.KerberosTransportBase.PingAsync(DnsRecord record, CancellationToken cancellationToken) in D:\a\Kerberos.NET\Kerberos.NET\Kerberos.NET\Client\Transport\KerberosTransportBase.cs:line 194
--- End of inner exception stack trace ---
at TaskExtensions.GetFastestAsync[TSource,TResult](IEnumerable`1 source, Func`3 task, CancellationToken cancellationToken) in D:\a\Kerberos.NET\Kerberos.NET\Kerberos.NET\TaskExtensions.cs:line 40
at Kerberos.NET.Transport.KerberosTransportBase.SelectedPreferredInstance(String domain, String servicePrefix, IEnumerable`1 results, Int32 defaultPort) in D:\a\Kerberos.NET\Kerberos.NET\Kerberos.NET\Client\Transport\KerberosTransportBase.cs:line 185

Expected behavior
Random is selected if all pings fail (+automatically select if only one is configured/available).

Preferably an option to disable fastest selection via PING.
Seems to have been introduced: 3bf4b3d

Additional
In our environment we have an extremely strict firewall that allows only and only the explicit connections (PING is not one them) so while we are able to connect to DC we are unable to PING them to figure out whether they are alive.

[SteveSyfuhs]

Yeah fair enough. I'll fix this asap.