Fix Extension Manager bug: a poorly-scoped jQuery call causes it to see
*all* Bootstrap tabs in the entire DOM as part of its tab set, so it will
crash if any such other tabs exist in the UI.

This was the only jQuery call in the Extension Manager code that wasn't
scoped down to $dlg (or used an equivalent parent selector).
Merge pull request #7559 from adobe/pflynn/ext-manager-jquery-fix

Fix Extension Manager crash when other Bootstrap tabs present in DOM