trivial: fu-common: fix fallback for esp-path if udisks missing
trivial: fu-common: fix fallback for esp-path if udisks missing

Fixes: #2803

hughsie/fwupd,hughsie/fwupd,hughsie/fwupd,hughsie/fwupd,fwupd/fwupd,fwupd/fwupd,fwupd/fwupd,fwupd/fwupd