tools: fix frr-reload for nbr deletion of no form cmds
When a bgp neighbor removed from associated to peer-group,
the neighbor is fully deleted, subsequent deletion of any
configuration related to the neighbor leads to failure
in frr-reload.
Handle any 'no neighbor ...' part of lines_to_del list
Testing:
Below first line would delete the neighbor swp1.10,
the existing code before the change handles to remove
config starts with 'neighbor swp1.10 ...' but not
'no neighbor swp1.10 ...'.