add new property for bgp

[dihan0604]

Description

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[markcowl]

Will this parameter value really come from the pipeline? What, exactly does LegacyMode mean?

[markcowl]

Please add at least one test for the new property

[dihan0604]

@markcowl, test added and updated help.xml for new parameters. The new field is to let server side know whether the server should main old behavior for the customer or change the behavior to new behavior. I am not sure whether we need value from the pipeline , I followed other parameters in our cmdlets.

[dihan0604]

@markcowl , the customer can get the object from getting a call and use it to other new or set call. In this case, we will need value from the pipeline, right? I also added the default value for this new parameter since it is an optional parameter and when the customer does not specify it, it will have a default value.

[markcowl]

@dihan0604 There are merge conflicts, please update

[dihan0604]

@markcowl , merge conflict addressed

[markcowl]

on demand run here: http://azuresdkci.cloudapp.net/view/1-AzurePowerShell/job/powershell-demand/1621/