vm/qvm-dom0-update: don't check for template updates here
vm/qvm-dom0-update: don't check for template updates here

Also use exit code 100 to notify updates existence (the same way as yum
check-update does).

woju/qubes-core-admin,QubesOS/qubes-core-admin,QubesOS/qubes-core-admin,marmarek/qubes-core-admin,marmarek/qubes-core-admin,woju/qubes-core-admin,woju/qubes-core-admin,marmarek/qubes-core-admin,QubesOS/qubes-core-admin,woju/qubes-core-admin