qemuDomainRemoveChrDevice: Deal with qemuDomainChrRemove() failure

qemuDomainRemoveChrDevice: Deal with qemuDomainChrRemove() failure

When cleaning up after removed device, qemuDomainChrRemove() is
called. But this may fail, in which case we successfully ignore
the failure and virDomainChrDefFree() the device anyway. While it
decreases our memory consumption, it's a bit too far, especially
if the next step is 'virsh dumpxml'. Then our memory consumption
decreases all the way down to zero as we crash.

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