pimd: Allow bridges and bonds to up and down

pimd: Allow bridges and bonds to up and down

Bridges and bonds when ifdowned are removed from
the kernel in it's entirety, while pim assumed
that interfaces were kept around in some fashion.

Basically when we had an ifdown event, for all ifchannels
on that interface delete from the OIF.  Also note
the fact that the vif has gone away and we need to
recreate it on the next ifup.

Ticket: CM-13896
Signed-off-by: Donald Sharp <sharpd@cumulusnetworks.com>