Fixed property-reset event not firing for default_dispvm global property
Fixed property-reset event not firing for default_dispvm global property

fixes QubesOS/qubes-issues#5977

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