RunPodSandbox should block unless client context is canceled

A call to RunPodSandbox should only return timeout if the operation has timed
out because the clients context deadline was exceeded. On client cancelation
it should return gRPC Canceled otherwise it should block until the sandbox has
exited.

Signed-off-by: Justin Terry (VM) <juterry@microsoft.com>

pkg/server/sandbox_stop_test.go

@@ -62,7 +62,12 @@ func TestWaitSandboxStop(t *testing.T) {
 			cancel()
 			ctx = cancelledCtx
 		}
-		err := c.waitSandboxStop(ctx, sandbox, test.timeout)
+		if test.timeout > 0 {
+			timeoutCtx, cancel := context.WithTimeout(ctx, test.timeout)
+			defer cancel()
+			ctx = timeoutCtx
+		}
+		err := c.waitSandboxStop(ctx, sandbox)
 		assert.Equal(t, test.expectErr, err != nil, desc)
 	}
 }