Explicitely close files for recvfd client *after* they don't matter.

Previous we were allowing the recvfd files to be closed by their
finalizer and the GC.

This sometimes led to premature closing of files leading to errors like:

networkservicemesh/cmd-forwarder-vppagent#187

'Delete' case.  This fixes that by closing the files only after the
ctx has is Done.

Signed-off-by: Ed Warnicke <hagbard@gmail.com>

pkg/networkservice/common/mechanisms/recvfd/client.go

@@ -30,6 +30,7 @@ import (
 	"github.com/edwarnicke/grpcfd"
 
 	"github.com/networkservicemesh/sdk/pkg/networkservice/core/next"
+	"github.com/networkservicemesh/sdk/pkg/networkservice/core/trace"
 )
 
 type recvFDClient struct {
@@ -82,6 +83,14 @@ func (r *recvFDClient) Close(ctx context.Context, conn *networkservice.Connectio
 		inodeURLbyFilename: make(map[string]*url.URL),
 	})
 
+	go func(fileMap *perConnectionFileMap, conn *networkservice.Connection) {
+		<-ctx.Done()
+		for _, file := range fileMap.filesByInodeURL {
+			trace.Log(ctx).Infof("Closing file %q related to closed connection %s", file.Name(), conn.GetId())
+			_ = file.Close()
+		}
+	}(fileMap, conn)
+
 	// Whatever happens, clean up the fileMap
 	defer r.fileMaps.Delete(conn.GetId())