while the extension manager is querying via a dialog. Reuse
the isBusy for this.

Change-Id: I97572404ae296e87fd44711bf1e978bd5bad6280
Reviewed-on: https://gerrit.libreoffice.org/64161
Tested-by: Jenkins
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>