Fix wiki delete npe and hide datasource test button

[labkey-adam]

Rationale

Addressing two unrelated issues:

• Hide the data source "Test" button when in production mode. https://github.com/LabKey/internal-issues/issues/835
• Fix an NPE when "bad" parameters are passed to the wiki delete action.
  • Found by the TeamCity crawler: https://teamcity.labkey.org/buildConfiguration/LabKey_2511Release_Community_DailySqlServer/3839876?buildTab=overview
  • This URL reproduces the exception (and behaves better with the fix): wiki-delete.view?version=">%27>%27"<script>alert(%278(%27)<%2Fscript>
  • The NPE occurs because generic form binding fails (the form expects version to be an int data type) and the action code that always populates the _wiki instance var is never invoked
  • Returning null from getFailureURL() means the confirm action displays a generic view showing the error message