Convert Chtimes to a setstat call for reuse with other stat setting functions.
Convert Chtimes to a setstat call for reuse with other stat setting functions.

fuchsia-mirror/third_party-github.com-pkg-sftp,jtwatson/sftp,pkg/sftp,ScriptRock/sftp,fuchsia-mirror/third_party-pkg-sftp,akupas/sftp,DrJosh9000/sftp