PC-BSD/trueos 03537a1usr.sbin/pc-sysinstall/backend functions-unmount.sh functions-upgrade.sh

Update to pc-sysinstall for a few issues:

Use new 'efibootmgr' to set default EFI entry to boot, fixes boot on some systems which
don't respect BOOTx64.efi as default entry

Switch to loader.efi as default TrueOS loader, fixes issue with GOP settings being gone

Setup EFI boot on upgrade, fixes #235
DeltaFile
+25-6usr.sbin/pc-sysinstall/backend/functions-unmount.sh
+18-0usr.sbin/pc-sysinstall/backend/functions-upgrade.sh
+43-62 files

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