added sftp client implementation

vendor/github.com/pkg/sftp/server_statvfs_stubs.go

@@ -0,0 +1,15 @@
+// +build !darwin,!linux,!plan9
+
+package sftp
+
+import (
+	"syscall"
+)
+
+func (p *sshFxpExtendedPacketStatVFS) respond(svr *Server) responsePacket {
+	return statusFromError(p.ID, syscall.ENOTSUP)
+}
+
+func getStatVFSForPath(name string) (*StatVFS, error) {
+	return nil, syscall.ENOTSUP
+}