Replace netievent lock-free queue with simple locked queue

Replace netievent lock-free queue with simple locked queue

The current implementation of isc_queue uses Michael-Scott lock-free
queue that in turn uses hazard pointers.  It was discovered that the way
we use the isc_queue, such complicated mechanism isn't really needed,
because most of the time, we either execute the work directly when on
nmthread (in case of UDP) or schedule the work from the matching
nmthreads.

Replace the current implementation of the isc_queue with a simple locked
ISC_LIST.  There's a slight improvement - since copying the whole list
is very lightweight - we move the queue into a new list before we start
the processing and locking just for moving the queue and not for every
single item on the list.

NOTE: There's a room for future improvements - since we don't guarantee
the order in which the netievents are processed, we could have two lists
- one unlocked that would be used when scheduling the work from the
matching thread and one locked that would be used from non-matching
thread.

(cherry picked from commit 6bd025942c4aeef42ef06f380a70c70acf490b1d)