chore(testproxy): Resolve the TestMutateRows_Generic_CloseClient conformance test (#1559)

* Test proxy should not mask error sent back

* chore(testproxy): Resolve the TestMutateRows_Generic_CloseClient conformance test

* Address the known failure

* Add the generic close client known failure back

* 🦉 Updates from OwlBot post-processor

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

---------

Co-authored-by: Kevin Kim <kevkim@google.com>
Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

Author: 3 people

protos/protos.d.ts

@@ -1,6 +1,5 @@
 TestMutateRow_Generic_DeadlineExceeded\|
 TestMutateRow_Generic_CloseClient\|
-TestMutateRows_Generic_CloseClient\|
 TestMutateRows_Retry_WithRoutingCookie\|
 TestReadRow_Generic_DeadlineExceeded\|
 TestReadRow_Retry_WithRoutingCookie\|

protos/protos.js

@@ -48,7 +48,7 @@ const bulkMutateRows = ({clientMap}) =>
         : [];
       return {
         status: {
-          code: error.code,
+          code: error.code ? error.code : grpc.status.UNKNOWN,
           details: [],
           message: error.message,
         },