TcpClient.Connect throws NRE if the Socket is cleared #69493
Description
After #67951, the Connect_DnsEndPoint_Success(mode: 1) TcpClient outerloop test is failing with an NRE.
System.NullReferenceException : Object reference not set to an instance of an object.
at System.Net.Sockets.TcpClient.Connect(String hostname, Int32 port) in /_/src/libraries/System.Net.Sockets/src/System/Net/Sockets/TCPClient.cs:line 130
at System.Net.Sockets.Tests.TcpClientTest.Connect_DnsEndPoint_Success(Int32 mode) in /_/src/libraries/System.Net.Sockets/tests/FunctionalTests/TcpClientTest.cs:line 222
at System.RuntimeMethodHandle.InvokeMethod(Object target, Void** arguments, Signature sig, Boolean isConstructor)
at System.Reflection.RuntimeMethodInfo.InvokeNonEmitUnsafe(Object obj, IntPtr* arguments, Span`1 argsForTemporaryMonoSupport, BindingFlags invokeAttr) in /_/src/coreclr/System.Private.CoreLib/src/System/Reflection/RuntimeMethodInfo.CoreCLR.cs:line 387
The _clientSocket is only initialized during the ctor, so the Connect ends up failing if the user clears the Client socket manually.
cc: @wfurt