do_uefiapp_deploy copies files into the /boot directory of the rootfs
and thus, like do_rootfs, should run under pseudo so that the files
end up being owned by root.

This did not trigger the uid leak check, perhaps because the task runs
later.

For some (still unknown reason), sometimes the installed files did end
up being owned by root, which tripped up a swupd test because the
system update randomly included unexpected changes to bootx64.efi or
rmc.db. With this change, they are owned by root consistently.

Signed-off-by: Patrick Ohly <patrick.ohly@intel.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>