Cancel display on linger timeout if exceptional ui state is restarted

Before the fix exceptional ui state stack could get collapsed prematurely
due to previously scheduled linger timeout, leaving the display state
management out of sync with what is happening on the ui side.

[mce] Cancel display on linger timeout if exceptional ui state is restarted. Fixes JB#18788
Merge pull request #159 from spiiroin/cancel_linger_timeout

Cancel display on linger timeout if exceptional ui state is restarted