Bc Group population during cluster reboot

Bc Group population during cluster reboot

these changes make sure that during cluster reboot scenario,
bc groups remain intact as they were before cluster reboot.

as the elan interfaces gets replayed elan broadcast group
gets reconstructed from scratch and as the final elan interface is added
elan broadcast group will become identical to what it was before cluster
reboot.

During this period where bc group starts with 1 bucket and reaches to
the correct no of buckets the broadcast traffic will be affected.

while doing bc group update, instead of replacing the group with new set
of buckets , first read existing buckets and add the new buckets to
existing buckets.

Change-Id: I111a9efa6c354724681ea4e7fc76cb6f37ba7f1e
Signed-off-by: manojna v <manojna.vijayakrishna@ericsson.com>