PROBLEM:
When large number of connections are continuously made
with wait_timeout of 600 seconds for  some hours, some
connections remain after wait_timeout expired and also
new connections get struck under the configuration and
the scenario reported in bug#16196591.
FIX:
The cause of this bug is the issue identified  and fixed in
the BUG#16088658 in 5.6.Also LOCK_thread_count contention 
issue fixed in BUG#15921866 in 5.6 need to be in 5.5 as 
well. Since the issue is not reproducible, it has been
verified at customer configuration the issue could not
be reproduced after a 48-hour test with a non-debug build               
which includes the above two fixes backported.