check handle before shutdown in quic connection Dispose

[wfurt]

fixes observed NRE failure in CI
https://helixre8s23ayyeko0k025g8.blob.core.windows.net/dotnet-runtime-refs-pull-55877-merge-4b55bf7e17664f8d97/System.Net.Http.Functional.Tests/console.44cb6dd0.log?sv=2019-07-07&se=2021-08-09T20%3A59%3A05Z&sr=c&sp=rl&sig=fcVOgCzStvmdaDVp%2FQRDS0Df0FtzBFqHVkrAh4pCysk%3D

      Condition(s) not met: "CanTestCertificates"
Unhandled exception. System.ArgumentNullException: SafeHandle cannot be null. (Parameter 'pHandle')
   at System.StubHelpers.StubHelpers.SafeHandleAddRef(SafeHandle pHandle, Boolean& success) in /_/src/coreclr/System.Private.CoreLib/src/System/StubHelpers.cs:line 1273
   at System.Net.Quic.Implementations.MsQuic.MsQuicConnection.Dispose(Boolean disposing) in /_/src/libraries/System.Net.Quic/src/System/Net/Quic/Implementations/MsQuic/MsQuicConnection.cs:line 715
   at System.Net.Quic.Implementations.MsQuic.MsQuicConnection.Finalize() in /_/src/libraries/System.Net.Quic/src/System/Net/Quic/Implementations/MsQuic/MsQuicConnection.cs:line 684
./RunTests.sh: line 162:    22 Aborted                 (core dumped) "$RUNTIME_PATH/dotnet" exec --runtimeconfig System.Net.Http.Functional.Tests.runtimeconfig.json --depsfile System.Net.Http.Functional.Tests.deps.json xunit.console.dll System.Net.Http.Functional.Tests.dll -xml testResults.xml -nologo -nocolor -notrait category=IgnoreForCI -notrait category=OuterLoop -notrait category=failing $RSP_FILE
/root/helix/work/workitem
----- end Tue Jul 20 21:05:32 UTC 2021 ----- exit code 134 ----------------------------------------------------------
exit code 134 means SIGABRT Abort. Managed or native assert, or runtime check such as heap corruption, caused call to abort(). Core dumped.

When constructor for outbound connection fail, _state.Handle can be null and this would be called from finalizer.

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Issue Details

---

fixes observed NRE failure in CI
https://helixre8s23ayyeko0k025g8.blob.core.windows.net/dotnet-runtime-refs-pull-55877-merge-4b55bf7e17664f8d97/System.Net.Http.Functional.Tests/console.44cb6dd0.log?sv=2019-07-07&se=2021-08-09T20%3A59%3A05Z&sr=c&sp=rl&sig=fcVOgCzStvmdaDVp%2FQRDS0Df0FtzBFqHVkrAh4pCysk%3D

      Condition(s) not met: "CanTestCertificates"
Unhandled exception. System.ArgumentNullException: SafeHandle cannot be null. (Parameter 'pHandle')
   at System.StubHelpers.StubHelpers.SafeHandleAddRef(SafeHandle pHandle, Boolean& success) in /_/src/coreclr/System.Private.CoreLib/src/System/StubHelpers.cs:line 1273
   at System.Net.Quic.Implementations.MsQuic.MsQuicConnection.Dispose(Boolean disposing) in /_/src/libraries/System.Net.Quic/src/System/Net/Quic/Implementations/MsQuic/MsQuicConnection.cs:line 715
   at System.Net.Quic.Implementations.MsQuic.MsQuicConnection.Finalize() in /_/src/libraries/System.Net.Quic/src/System/Net/Quic/Implementations/MsQuic/MsQuicConnection.cs:line 684
./RunTests.sh: line 162:    22 Aborted                 (core dumped) "$RUNTIME_PATH/dotnet" exec --runtimeconfig System.Net.Http.Functional.Tests.runtimeconfig.json --depsfile System.Net.Http.Functional.Tests.deps.json xunit.console.dll System.Net.Http.Functional.Tests.dll -xml testResults.xml -nologo -nocolor -notrait category=IgnoreForCI -notrait category=OuterLoop -notrait category=failing $RSP_FILE
/root/helix/work/workitem
----- end Tue Jul 20 21:05:32 UTC 2021 ----- exit code 134 ----------------------------------------------------------
exit code 134 means SIGABRT Abort. Managed or native assert, or runtime check such as heap corruption, caused call to abort(). Core dumped.

When constructor for outbound connection fail, _state.Handle can be null and this would be called from finalizer.

Author:	wfurt
Assignees:	wfurt
Labels:	area-System.Net.Quic
Milestone:	-

[wfurt]

failing test is #55957