Fix the crash on creating a Hyper Tree Grid source.

The crash was due to a bad IntVectorProperty command call for
the vtkHyperTreeGridSource source proxy.
SetAxisBranchFactor is now called SetBranchFactor.

Change-Id: I82ee4cf56f3b7e31f0a403055cbc93d4c3ce7384
Merge topic 'FixCrashOnHyperTreeGridSource' into next

37b6bff Fix the crash on creating a Hyper Tree Grid source.