Query the enumeration of instances of the class (and subclasses) defined by reference op using the query expression.
Arguments are the client object pointer cl, an ObjectPath object pointer op with the reference that contains namespace and classname compo-
nents, the query expression string pointer in query, the query language identifier string pointer in lang, and rc which returns the opera-
tion status (suppressed when NULL).
When successful the CMCIClientFT.execQuery() function returns a pointer to a CMPIEnumeration object that contains the class instances that
match the query and sets a successful operation status code. When unsuccessful it returns a NULL pointer and sets the operation status
error code and corresponding error string in rc.