[202205][show]Fix show route return code on error

[dgsudharsan]

Porting of changes #2542 to 202205

What I did

Fix show route return command to return error code on failure cases. The parameter return_cmd=True in run_command will suppress the return code and return success even in error scenarios.

How I did it

When run command is called with return_cmd = True, modified its return to include return code, which can then be used to assess if there is an error by the caller

How to verify it

Added UT to verify it

Previous command output (if the output of a command-line utility has changed)

root@sonic:/home/admin# show ip route 123
% Unknown command: show ip route 123 

root@sonic:/home/admin# echo $?
0

New command output (if the output of a command-line utility has changed)

root@sonic:/home/admin# show ip route 123
% Unknown command: show ip route 123 

root@sonic:/home/admin# echo $?
1

[dgsudharsan]

/azpw run Azure.sonic-utilities

[mssonicbld]

/AzurePipelines run Azure.sonic-utilities

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Azure Pipelines successfully started running 1 pipeline(s).

[liat-grozovik]

/azp run Azure.sonic-utilities

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Azure Pipelines successfully started running 1 pipeline(s).

[yxieca]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).