Drop log.DBusHandler
Drop log.DBusHandler

Packages had missing dependency on python-dbus. Since DBusHandler isn't
used anywhere, drop it, instead of introducing more dependencies.

Reported by @pietrushnic
QubesOS/qubes-issues#3179

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