Connmgr fixups

- Replace list+explicit counter with new 'clist'
- Replace timer_create/destroy with rearm/disarm
- Added dump function to print pool state to stderr
- Added 'lcb_async_signal' and 'lcb_async_cancel' to timer.h

Change-Id: Ibd2eaee63dbd4be24f5c1096b3c45d3edc265d0f
Reviewed-on: http://review.couchbase.org/33112
Reviewed-by: Brett Lawson <brett19@gmail.com>
Tested-by: Mark Nunberg <mnunberg@haskalah.org>