Merge topic 'ep-update-disconnected'

8cc45e150a ExternalProject: Make hg download method respect UPDATE_DISCONNECTED
1512dc43cb ExternalProject: Avoid reconfigure when updates are disconnected
1d29cf37a1 Tests: Reduce warning noise in ExternalProjectUpdate test

Acked-by: Kitware Robot <kwrobot@kitware.com>
Merge-request: !8498