[DNS] Issues with 'az network dns record-set show'

[jtuliani]

Issues with 'az network dns record-set show':

• 1. If record set does not exist, error message says The resource record 'cccnamed' does not exist in resource group 'rg1' of subscription ''. This error also needs to list the zone name.
• 2. In some cases (e.g. showing the SOA at the zone apex via az network dns record-set show -g rg1 -n "@" --type SOA --zone-name jt-test.com), I just get a red message 'Failed to open file' and no record set is shown (PR Fix issues with @syntax #1581)
• 3. When showing, do not include all the 'null' objects for other record types in the JSON output. ([Network] DNS Fixes Round 2 #1592)
• 4. Needs short form for --zone-name (-z) and --type (-t) (PR [DNS] Issues with 'az network dns record-set create' #1129)

[JasonRShaver]

• add zone name to error (does service return zone name?)
• add support for DNS-style @ sign
• add -z and -t

service returns nulls for #3, how do we know what to filter? Is service side filtering a possibliity

[jtuliani]

See #1131 for example of current record set output format, plus desired record set output format.

[tjprescott]

IRT item 1, this is the error returned from the service. If it is inadequate, it should be updated there.

[jtuliani]

Re #1, yes, I believe we already have a service bug for this, good point.