qemuDomainNamespaceTeardownHostdev: Unlink paths in one go

qemuDomainNamespaceTeardownHostdev: Unlink paths in one go

In my attempt to deduplicate the code, we can use
qemuDomainSetupHostdev() to obtain the list of paths to unlink
and then pass it to qemuDomainNamespaceUnlinkPaths() to unlink
them in a single fork.

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