Ticket 48882 - server can hang in connection list processing
Bug Description: if a thread holding the connection monitor
is stuck in polling and the client doesn't
respond, the main thread can be blocked on
this connection when iterating the connection
table.
Fix Description: Implement a test and enter function for the connection
monitor, so the main thread will never wait for a
connection monitor already owned by an other thread
https://fedorahosted.org/389/ticket/48882
Reviewed by: Noriko, Thanks
(cherry picked from commit 7110db91e75f392f1c83643d9aa88895992d9c01)