[Libvirt-cim] [PATCH 0 of 3] #2 - Check client given object pathes in ElementCapabilities provider

To enable the check for the client's given object path in ElementCapabilities, changes to the ComputerSystem and AllocationCapabilities provider have been necessary. Diff to patch #1: - added a new function to libcmpiutil - cu_validate_ref(ref, inst) - that does the check between the system instance and the client given instance - get_domain() is now using the new libcmpiutil function - the parameter CMPIInstance **inst is now used to "configure" get_domain(); for internal usage the inst is returned and for external usage this can be ignored by setting it to NULL - validate_domain_ref() is now only an interface name for the client - removed patch unrelated changes in patch 2 - reworked logic to return instance(s)