azure-pipelines-tasks: Variable substitution for ApplicationSettings not working

It seems that while appSettings are correctly substituted, applicationSettings are not.

Her in xmlvariablesubstituionutility.ts the code is iterating through a set of tags.

https://github.com/Microsoft/vsts-tasks/blob/a698fb593f58fe733df94aa166a99ed3ea6dda5b/Tasks/Common/webdeployment-common/xmlvariablesubstitutionutility.ts#L84

There appears to be special case code for configSections and connectionStrings https://github.com/Microsoft/vsts-tasks/blob/a698fb593f58fe733df94aa166a99ed3ea6dda5b/Tasks/Common/webdeployment-common/xmlvariablesubstitutionutility.ts#L125

and the rest of the code goes to updateXmlNodeAttribute https://github.com/Microsoft/vsts-tasks/blob/a698fb593f58fe733df94aa166a99ed3ea6dda5b/Tasks/Common/webdeployment-common/xmlvariablesubstitutionutility.ts#L178

It looks like updateXmlNodeAttribute is really designed for appSettings structures as:

<appSettings>
<add key="blat" value="blart"/>
</appSettings>

and not applicationSettings structures which look like:

<applicationSettings>
  <myCustomSection>
   <setting name="blat" serializeAs="String">
      <value>blart</value>
   </setting>
  </myCustomSection>
</applicationSettings>