Modify MultSlice tests for new default view.

Since now we have three slices (X,Y,Z) based on center of the dataset, the
create slice event was removed to simplify the testing results due to
variance in detecting mouse click postions on different machines.

Change-Id: Ie179f3b517150d98f90718119842277d56c69e29
Merge topic '13872_sliceview_default' into next

f648756 Modify MultSlice tests for new default view.