Pie controls: Fix event handling on chained input filters

Enabling accessibility helpers like "Magnification gestures" while
pie controls are active will result in a system reboot. After this
every input event (touch/key) will cause a system restart directly.

This commit fixes this, by making semantics for
sendInputEvent() with one filter equal to the case where more than
one input filter is installed.

Change-Id: Ie8a319e8c9a63c82c77122332c7d5dd71672cc75