[sctp] port sctp to the new API and fix many issues

• use the new transport API
• fix locking context around to avoid race conditions and deadlocking
• fix shutdown code (segfaults and core dumps)
• properly differentiate between connecting sockets and accepted sockets and better use of fd_tracker
• abstract as much as possible socket management code from threads
• add lots of comments and debugging messages around
• simplify socket error management reported from RX thread
• rework loop timers for connect_thread to avoid thread overload
• reduce usage of _transport_addrtostr to one call and reuse link information around
• improve error handling across the board
• stop using data structs inside epolls and switch back to using fds this was necessary to avoid processing stale data from epolls and look up data from fd_tracket instead
• add listener stop function
• make functions safer to be called multiple times
• probably more.. but can't remember

Signed-off-by: Fabio M. Di Nitto <fdinitto@redhat.com>