test: simplify the helper for moving three touches at the same time

test: simplify the helper for moving three touches at the same time

There's no test case where we need to do something immediately after the last
event so we might as well do everything in the same loop.

This also fixes a bug where the first movement would usually get swallowed.
Test cases in general put the finger down at x/y, then move them to some other
position. We'd expect the first event in a loop to happen at x+n/y+n, not at
x/y again.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>