tools: fix frr-reload multiple no description cmds

tools: fix frr-reload multiple no description cmds

Ensure to change description for index 0 from the list.

Ticket: #3628756
Testing Done:

After fix:
start with three interfaces description delete in lines_to_del:
(Pdb) lines_to_del
[(('interface swp1',), "description swp1 -> sp1's swp1"),
(('interface swp2',), "description swp2 -> sp2's swp
1"), (('interface swp3',), "description swp3 -> sp3's swp1")]

After first iteration swp1:
(Pdb) index
0
(Pdb) lines_to_del
[(('interface swp1',), 'description'), (('interface swp2',),
"description swp2 -> sp2's swp1"), (('interface swp
1s2',), "description swp3 -> sp3's swp1")]

After second iteration swp2:
(Pdb) lines_to_del
[(('interface swp1',), 'description'), (('interface swp2',),
'description'), (('interface swp3',), "description
swp3 -> sp3's swp1")]

After third iteration swp3 fix
(Pdb) lines_to_del
[(('interface swp1',), 'description'), (('interface swp2',),
'description'), (('interface swp3',), 'description'
)]

Signed-off-by: Chirag Shah <chirag@nvidia.com>
(cherry picked from commit 8a5c6e4389a8f56c1a25941977a1f6acaf92f53e)