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)
    (cherry picked from commit 19c4638f689e88ebc1eaec030039d2a4521aa7c4)