testing: Add dropped argument for MultiServer tests

Change-Id: I08fc0dcef007798229ee9241f8134f0ab69134b7
testing: Add missing data files

Change-Id: Iee69c6533b131d66177747384e959ab73292252c
cmake: Copy ExternalData files from VTK

They aren't present in older CMake versions and must be provided
manually.

Change-Id: I57f6301e4e881be49c27bb110957fad290a6442b
testing: Look for objects in the hook storage directory

Change-Id: I39c2e75e41eb6e06d0770371bd1f95b841c5306b
testing: Append to the URL templates

Change-Id: Ic27f74640277e675350b0c24e67112242ff9b092
testing: Update data references

Change-Id: Ib6a02e534dbf374cba12f2e8214ab8c5c96a80d5
Merge topic 'use-external-data' into next

d96bc809 testing: Update data references
8d96007f testing: Append to the URL templates
ec803c3c testing: Look for objects in the hook storage directory
398e074f cmake: Copy ExternalData files from VTK
c0c63f74 testing: Add missing data files
c3f647db testing: Add dropped argument for MultiServer tests