add arista failed pattern

[alsigna]

Hi,

In case of duplicated seq of prefix-list, arista writes % Duplicate sequence number which is not element of FAILED_WHEN_CONTAINS list for arista driver. This PR adds missed error message.

switch(config)#ip prefix-list pl_TEST seq 10 permit 192.168.0.0/24
switch(config)#do sh ip prefix-list pl_TEST
ip prefix-list pl_TEST seq 10 permit 192.168.0.0/24

switch(config)#ip prefix-list pl_TEST seq 10 permit 10.0.0.0/24
% Duplicate sequence number

switch(config)#do sh ip prefix-list pl_TEST
ip prefix-list pl_TEST seq 10 permit 192.168.0.0/24
switch(config)#

[carlmontanari]

LGTM! 🔥