Move restoration of old umask to a defer

Suggested in comment on PR #941

Signed-off-by: Jonathon Anderson <janderson@ciq.com>

internal/pkg/configure/tftp.go

@@ -15,11 +15,11 @@ func TFTP() (err error) {
 	controller := warewulfconf.Get()
 	var tftpdir string = path.Join(controller.TFTP.TftpRoot, "warewulf")
 	oldMask := unix.Umask(0)
+	defer unix.Umask(oldMask)
 	err = os.MkdirAll(tftpdir, 0755)
 	if err != nil {
 		return
 	}
-	_ = unix.Umask(oldMask)
 
 	if controller.Warewulf.GrubBoot {
 		err := warewulfd.CopyShimGrub()