We must also remember to free nvlists added to a parent nvlist with
nvlist_append_nvlist_array().

More importantly, when nvlist_pack() allocates memory for us it does so
in the M_NVLIST zone, so we must free it with free(.., M_NVLIST). Using
free(.., M_TEMP) as we did silently failed to free the memory.

MFC after: 3 days
Repored by: kib@
Sponsored by: Rubicon Communications, LLC ("Netgate")