Fixed NullReferenceExcepton in Socket.Connect for non-IP endpoints

Socket.Connect(EndPoint) throws a NullReferenceException when connecting to non-IP (eg Unix) endpoints in Dgram mode.
[WCF] Disable CloseTest and OpenTest4 in CustomPeerResolverServiceTest.

These tests occasionally time out:

Test Case Failures:
1) MonoTests.System.ServiceModel.PeerResolvers.CustomPeerResolverServiceTest.CloseTest : System.TimeoutException : The operation has timed-out.
at System.ServiceModel.Channels.HttpRequestChannel+HttpChannelRequestAsyncResult.WaitEnd () [0x00000] in <filename unknown>:0
at System.ServiceModel.Channels.HttpRequestChannel.EndRequest (IAsyncResult result) [0x00000] in <filename unknown>:0
at System.ServiceModel.Channels.HttpRequestChannel.Request (System.ServiceModel.Channels.Message message, TimeSpan timeout) [0x00000] in <filename unknown>:0
at System.ServiceModel.MonoInternal.ClientRuntimeChannel.Request (System.ServiceModel.Channels.Message msg, TimeSpan timeout) [0x00000] in <filename unknown>:0
at System.ServiceModel.MonoInternal.ClientRuntimeChannel.Request (System.ServiceModel.Description.OperationDescription od, System.Object[] parameters) [0x00000] in <filename unknown>:0
at System.ServiceModel.MonoInternal.ClientRuntimeChannel.DoProcess (System.Reflection.MethodBase method, System.String operationName, System.Object[] parameters) [0x00000] in <filename unknown>:0
at System.ServiceModel.MonoInternal.ClientRuntimeChannel.Process (System.Reflection.MethodBase method, System.String operationName, System.Object[] parameters) [0x00000] in <filename unknown>:0

I.e. we're timing out waiting for the async wait handle here: https://github.com/mono/mono/blob/master/mcs/class/System.ServiceModel/System.ServiceModel.Channels/HttpRequestChannel.cs#L495

Since we have no current WCF maintainer and this is deep, deep within
WCF land and causes unstable builds on Jenkins, disable these tests
for now.

Bug: https://bugzilla.xamarin.com/show_bug.cgi?id=21069
[System] Add more logging to the BeginConnectMultiple test.
Revert "[corlib] Re-enable TaskContinuationChainLeak test."

This reverts commit 265060cc22a863326d68cef3d0c79998bac37fc7.

The test is still failing:

2) MonoTests.System.Threading.Tasks.TaskTests.TaskContinuationChainLeak :   Expected: False
  But was:  True

at MonoTests.System.Threading.Tasks.TaskTests+TaskContinuationChainLeakTester.Verify () [0x00000] in /var/lib/jenkins/workspace/Mono/mcs/class/corlib/Test/System.Threading.Tasks/TaskTest.cs:1991
at MonoTests.System.Threading.Tasks.TaskTests.TaskContinuationChainLeak () [0x00022] in /var/lib/jenkins/workspace/Mono/mcs/class/corlib/Test/System.Threading.Tasks/TaskTest.cs:1948
at (wrapper managed-to-native) System.Reflection.MonoMethod:InternalInvoke (System.Reflection.MonoMethod,object,object[],System.Exception&)
at System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) [0x00054] in /var/lib/jenkins/workspace/Mono/mcs/class/corlib/System.Reflection/MonoMethod.cs:230
[runtime] Enable aot on 64 bit osx.
[mcs] A value for params parameter with default valus is still empty array
[mcs] Use same result conversion rules of predefined enum operators for unary and binary expressions
[mcs] Methodgroup conversion involving user defined operators
[mcs] Methodgroup probing checks are not allowed
[mcs] Overload resolution should not fail when type inference infers inaccessible types but other overload exists
[mcs] Fixes flow analysis of if statement with constant expression
[mcs] Don't cache lambda expressions in static constructor context
[sdb] Add support for returning the changed valuetype receiver after invokes to valuetype methods.
[runtime] Use sleep (1) instead of sleep (0) in the native SIGSEGV suspend loop to reduce cpu usage.
Empty commit, poking Jenkins...
[corlib] Fix Delegate::DynamicInvoke for open delegates of instance methods and closed delegates of static methods
[sdb] Add support for out arguments in invokes.
[mcs] Allow more conversions for CallerLineNumberAttribute
[corlib] Update 6b94215d0b82c0a24786cb33ecce3f89d6c4d879 to work with not null targets too
Update the required bootstrap mono version to 2.10, 2.4 will no longer work.