Coverity: Resolve CHECKED_RETURN - get_dev_from_pool
Coverity: Resolve CHECKED_RETURN - get_dev_from_pool

(4) Event check_return:
    Calling function "cu_get_str_prop(CMPIInstance const *, char const *,
    char const **)" without checking return value (as is done elsewhere 72
    out of 77 times).
(11) Event unchecked_value:
    No check of the return value of "cu_get_str_prop(inst,
    "CreationClassName", &cn)".

118                     cu_get_str_prop(inst, "CreationClassName", &cn);
119                     cu_get_str_prop(inst, "DeviceID", &dev_id);
120
121                     if ((dev_id == NULL) || (cn == NULL))
122                             continue;

Resolve by making proper check of function return vs. CMPI_RC_OK and removing
the NULL checks since they are redundant.

libvirt/libvirt-cim,libvirt/libvirt-cim,libvirt/libvirt-cim