zebra: Cleanup ptm memory *after* we tell the sockets to clean up

zebra: Cleanup ptm memory *after* we tell the sockets to clean up

The zebra_ptm_finish() code was being called before the
client_list deletion.  The client_list deletion is
attempting to call the ptm daemon and shut down the connection.
We should not be doing this *after* we shut down memory associated
with it as that we were writing into memory in random spots
in this case.

Signed-off-by: Donald Sharp <sharpd@cumulusnetworks.com>