LibevConnection: Fix timer cleanup.
LibevConnection: Fix timer cleanup.

The timer cleanup loop was modifying the dictionary that it is iterating
over.  The obvious fix is to just call keys() and iterate over its
result... hopefully the new key-view stuff doesn't cause a similar
breakage to occur.

vitaly-krugl/pika,knowsis/pika,pika/pika,Zephor5/pika,zixiliuyue/pika