tools/qvm-start-daemon: reduce required permissions to sys-gui itself
tools/qvm-start-daemon: reduce required permissions to sys-gui itself

Do not require permission to list sys-gui itself just to get keyboard
layout. Listing itself is not sensitive (sys-gui knows it exists), but
it will make other tools request its properties, which may not be
desirable.

marmarek/qubes-core-mgmt-client,marmarek/qubes-core-mgmt-client,marmarek/qubes-core-mgmt-client