parallels: fix possible crash in case of errors in prlsdkLoadDomain

parallels: fix possible crash in case of errors in prlsdkLoadDomain

Cleanup code in prlsdkLoadDomain doesn't take into account the fact
if private domain structure along with freeing function is assigned
or not. In case it is, we shouldn't call it manually because
virDomainObjListRemove calls it and frees pdom.
Also, allocated def structure should be freed only if it's not
assigned to domain. Otherwise it will be called twice: one time by
virDomainObjListRemove and the second by prlsdkLoadDomain itself.

Signed-off-by: Maxim Nestratov <mnestratov@parallels.com>