ch: Drop deadcode from chDomainDetachDeviceLive()

ch: Drop deadcode from chDomainDetachDeviceLive()

At the end of chDomainDetachDeviceLive() there's a code that
tries to remove the disk that's being detached from the domain
definition. Well, it's a leftover from the original patch which I
forgot to remove when rewriting it to use chDomainRemoveDevice().
The disk is removed there so this code has no chance in removing
it again. Drop the code.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>