When a nexthop group is modified do not assume that it
is not installed. The creation of the pnhgc is enough
to set the installed to false. If we are reinstalling
it is not needed to set it as not installed.
When a pbrms is being installed/removed check to see if it
is already installed/deleted and do the right thing from
there.
Ticket: CM-20371 Signed-off-by: Donald Sharp <sharpd@cumulusnetworks.com>