pimd: Fix show run output to be correct.

pimd: Fix show run output to be correct.

When issuing a vtysh -m command it expects the
output it receives to be the complete command
not a partial match.

The 'debug pim packets joins' command
was being outputted as 'debug pim packets join'

This was making quagga-reload.py unhappy.  Adding
the joins word allows it to complete successfully

Ticket: CM-13805
Signed-off-by: Donald Sharp <sharpd@cumulusnetworks.com>
Reviewed-by: Daniel Walton <dwalton@cumulusnetworks.com>