Stores entry in the keytab id. Fails if the entry already exists.
This operation must, within the constraints of the operating system, not return until it can verify that the write has completed succesfully. For example, in a UNIX file-based implementation, this routine (or the part of the underlying implementation that it calls) would be responsible for doing an fsync on the file before returning.
This routine should return an error code if entry is already present in the keytab or if the key could not be stored (quota problem, etc).
Searches the keytab id for an entry that exactly matches entry. If one is found, it is removed from the keytab.