zebra: set remoteseq to 0 when remote mac is deleted by bgpd

zebra: set remoteseq to 0 when remote mac is deleted by bgpd

When the remote mac is deleted by bgpd we can end up with an auto mac
entry in zebra if there are neighs referring to the mac. The remote sequence
number in the auto mac entry needs to be reset to 0 as the mac entry may
have been removed on all VTEPs (including the originating one).

Now if the MAC comes back on a remote VTEP it may be added with MM=0 which
 will NOT be accepted if the remote seq was not reset in the previous step.

Ticket: CM-22707

Signed-off-by: Anuradha Karuppiah <anuradhak@cumulusnetworks.com>
Signed-off-by: Vivek Venkatraman <vivek@cumulusnetworks.com>